bluuebunny/crossref_metadata_2025 huggingface dataset:
Mathematical model of a fountain with a water picture in the shape of an hourglass
Authors: Peszynski Kazimierz , Perczynski Daniel , Piwecka Lidia
Published: June 2019

The work presents a mathematical model of a fountain providing an hourglass-shaped water image based on four of its basic parameters: height H, coefficient of contraction χ, diameter of n nozzles arrangement Dna, and coefficient of contraction location σ. The developed model makes possible to determine the angle α specifying the slope of the nozzles to the horizontal plane and determining the remaining parameters of the fountain, especially its outer diameter Df as well as the diameter of the position of the stream tops Dmax. The developed model has been implemented in an Excel spreadsheet, which enables quick conversion of desired water images. The developed model works for n≤24 nozzles, however, derived dependencies allow for a quick extension of the model for n>24.
Cooling liquid flow boiling heat transfer in an annular minigap with an enhanced wall
Authors: Piasecka Magdalena , Musiał Tomasz , Piasecki Artur
Published: June 2019

The paper focused on flow boiling heat transfer in an annular minigap. This gap of 1 mm width was created between the metal pipe with an enhanced surface contacting fluid and the external glass pipe positioned along the same axis. The heated element for the HFE-649 flowing in the minigap was a cartridge heater. Thermocouples were used to measure the temperature of the metal pipe in the contact surface with a fluid. The local values of the heat transfer coefficient for stationary state conditions were calculated using an one-dimensional method in which the multilayer cylindrical wall was assumed to be planar. The results were presented as a function of the heat transfer coefficient along the minigap length and as boiling curves, prepared for selected values of mass flow rate and five types of the enhanced heated surface and a smooth one. Observations indicated that the highest local values of heat transfer coefficient were obtained with using the enhanced surface produced by electromachining process (spark erosion) at the saturated boiling region. The boiling curves generated for two distances from the minigap inlet have similar plots without a drop in the temperature of the heated surface characteristic for nucleation hysteresis.
Instability of a homogeneous flow from a lumped source in the presence of special boundary conditions on a free surface
Authors: Shmyrova Anastasia , Shmyrov Andrey
Published: June 2019

In this work, experimental studies were carried out to investigate the structure of a surface flow and to understand potential mechanisms leading to the formation of this type instability. The surface flow was generated by feeding water through three sources: a lumped source with free upper boundary, a slot gap, and a lumped source for inducing a capillary-driven Marangoni flow. For flow visualization, a traditional light knife technique was used. The application of a method of spatial separation of the water volume into two isolated parts whose common surface remained unchanged and the realization of a reverse situation with a divided surface made it possible to study in detail the surface flow structure and to determine the conditions for the appearance of such hydrodynamic instability. It is shown that the formation of a vortex flow is caused by the interaction between the coordinate of the flow homogeneous along the transverse flow and the layer of a surface-active substance adsorbed at the interface. The obtained experimental results demonstrate the importance of setting different boundary conditions for potential and vortex velocity components of a convective flow in the region near the interface occupied by a surfactant.
Design of a high-specific speed turbine with non-uniform blade cascade
Authors: Stareček Jakub , Čupr Pavel , Haluza Miloslav
Published: June 2019

This paper presents the hydraulic design of Kaplan type turbine in fully axial configuration. The turbine model consists of a straight pipe intake, a rib which covers the shaft, five axial guide vanes, a six blade runner and a 10,6°-full angle draft tube. Due to the presence of non-uniform velocity field behind the rib and interaction between stator and rotor, the pressure pulsations occur and cause some excitation forces acting on the runner. To reduce these negative phenomena the six non-uniform blade runner has been designed using computational fluid dynamics modelling (CFD). The runner blades are placed in various axial distances from the guide vanes. This new design should reduce the pressure pulsations caused by interaction between the rib and the runner, which is the main negative effect by the current design. The forces and torque which are acting on the runner blades as well as the pressure inside the turbine are observed in time domain. The amplitudes and frequencies are analysed using Fast Fourier Transform (FFT). The frequencies are compared to the modal analysis results of the runner submerged in water. This hydraulic design is based on previous axial turbine, which was designed for small hydro power plant located at Lužnice River. The design point is defined by head H = 1,5 m, volumetric flow rate Q = 2,1 m3/s and RPM n = 260 min-1. This turbine was designed using six runner blades to reduce the pressure, force and torque pulsations caused mainly by wakes, which were observed behind the rib.
On the boundary layer structure on suction side of an airfoil
Authors: Uruba Václav , Procházka Pavel , Skála Vladislav
Published: June 2019

The structure of boundary layer on an airfoil suction side was studied using stereo time resolved PIV technique experimentally in low Reynolds number, about 33 thousands. The mean velocity field is close to the 2D case, however the instantaneous structure is highly dynamical and 3D. Dynamics of the vortices in the boundary layer has been analysed using POD method. The results show lag of coherence in the streamwise direction, oblique patterns are detected instead.
On the global flow-field dynamics around an airfoil
Authors: Uruba Václav , Procházka Pavel , Skála Vladislav
Published: June 2019

The global flow-field around an airfoil will be studied using time-resolved PIV technique. Interactions between pressure and suction sides flows will be studied in detail. Spanwise structures dynamics is to be analysed.
First testing experiments with measurement of pool boiling heat transfer coefficient on a new apparatus
Authors: Vajc Viktor , Dostál Martin
Published: June 2019

We have designed a simple apparatus for measurement of heat transfer during pool boiling in order to find or create suitable correlations for heat-transfer coeﬃcient, which could be used for various liquids and conditions. We have run several testing experiments with tap and deionized water. This contribution presents proceedings and the first results of these experiments as well as comparison of these results with some published and verified correlations.
Turbulence Models for Simulation of the Flow in a Rotor-Stator Cavity
Authors: Zemanová Lucie , Rudolf Pavel
Published: June 2019

Modelling of the flow in the cavities between rotor and stator in turbomachines (e.g. pumps or turbines) is a task of great interest. Correctly evaluated pressure and velocity fields enable calculation of the disk losses and therefore assessment of efficiency. It is also crucial for determination of axial thrust and thus design of the bearings. The study demonstrates abilities of various turbulence models to describe the flow in a narrow gap between rotating and stationary disks. Numerical simulations were performed in order to find out the ability of particular models to capture unstable structures appearing during specific operating conditions as well as to calculate the velocity profiles precisely. Large Eddy Simulation (LES), Scale Adaptive Simulation (SAS), Detached Eddy Simulation (DES), Reynolds stress model (RSM) and SSTk–ωmodel were used. Obtained results were also compared with experimental measurement published by Viazzo et al. [1]
Analysis and interpretation of radiometric signals in a liquid-gas bubble flow
Authors: Zych Marcin , Hanus Robert , Jaszczur Marek , Golijanek-Jędrzejczyk Anna , Świsulski Dariusz , Roshani Gholam H.
Published: June 2019

The article presents the analysis of signals from a radiometric system consisting of two scintillation probes and two gamma radiation sealed sources. Calculations and interpretation were carried out for the bubble flow of the water-air mixture in the horizontal pipeline. The analysis of the obtained signals was done in time and frequency domain. In the frequency domain, a range of usable frequencies was identified, which were associated with changes in gamma-ray intensity recorded in the time domain. The gas phase velocity, void fraction and statistical parameters of the signal were also calculated.
A novel architecture of fibre-optic interferometric hydrophone
Authors: Huang Xiaodi , Chen Desheng
Published: June 2019

The fibre-optic interferometric hydrophone has been widely used in ocean acoustic applications. There are many different hydrophone systems in use. They can generally be classified as hull mounted, towed, or fixed (bottom mounted and vertical) array systems. Different optical architectures have evolved for each of the areas, which make a good case study on what aspects of a particular application influence the optical architecture. A novel architecture of fibre-optic hydrophone based on PMDI is theoretically and experimentally discussed in this paper. A novel optical configuration is proposed, and the modulation and demodulation system is built. A series of experiments are designed to analyse the characteristics of this system. The results of the experiments show that this type of fibre-optic interferometric hydrophone array has many advantages such as low noise, a large dynamic range.
Transverse horizontal spatial coherence in shallow water
Authors: Zhang Bo , Li Fenghua , Li Zhenglin , Zhang Yanjun , Wang Jingyan
Published: June 2019

Since the advent of large-aperture array processing, more and more attention has been paid to the sound field correlation, which has fundamental limit to the array gain of spatial coherent signal processing. The two dominant mechanisms that degrade the spatial coherence are normal modes (or multi-paths) interference and the environmental variability caused by several relevant oceanographic processes. In the present study, the transverse horizontal spatial coherence of explosive signals has been studied experimentally by a bottom-mounted array in the Northern South China Sea. And the effects of normal mode interference on the transverse horizontal spatial coherence have been analyzed numerically. Expressed in terms of wavelengths, the coherence length is shown to be larger than 170λ/185λ at acoustic frequency 508-640Hz/80-101Hz in shallow water. It is much greater than Carey’s shallow-water result 30λ estimated from array signal gain after assuming a specific functional form for the coherence (The Journal of the Acoustical Society of America 104, 831 (1998)). It, however, is consistent with Rouseff’s modelling result of a coherence length larger than 100λ (The Journal of the Acoustical Society of America 138, 2256 (2015)). Both Carey and Rouseff argue that the transverse horizontal spatial coherence length depends only weakly on range, in direct. In the present study, however, the coherence length is shown to depend highly on source-receiver range, and it fluctuates synchronously with the sound-field intensity while range varies.
The research of LWD acoustic isolator based on SAW spatial separation
Authors: Yang Peinian , Chen Dehua , Xiuming Wang
Published: June 2019

Acoustic logging while drilling (LWD) can extract P-wave and S-wave information from the formation. However, the transmission of the collar wave propagated directly from the emitter to the receiver may interfere with the P-wave and S-wave and affect the extraction of formation information. Therefore, it is necessary to design a suitable acoustic isolator between the transmitter and the receiver to attenuate the drill waves. The commonly used acoustic LWD isolator is that the outer surface of the drill collar is evenly grooved to attenuate the collar wave. However, there are still disadvantages such as the lack of mechanical strength of the evenly grooved acoustic insulators and the ability to extract clean longitudinal wave under certain circumstances. Therefore, there is an urgent requirement to design a new type of acoustic LWD isolator with sufficient strength and acoustic insulation requirements. In recent years, spoof surface acoustic waves (SSAWs) generated by periodic corrugated surface rigid plates have attracted the attention of many researchers, who can spatially separate the surface waves to attenuate acoustic waves. In this paper, a new type of acoustic LWD insulator based on SAW space separation structure is proposed. The finite element software ANSYS is used for acoustic analysis.
Acoustic scattering from a stiffened finite cylindrical shell with external rings
Authors: Zhou Fulin , Fan Jun , Wang Bin
Published: June 2019

Studying the interaction of sound with cylindrical shells immersed in water is essential and helpful to improving underwater target detection and classification algorithms. Elastic cylindrical shells often occur as part of double-layered shell and have been widely used in marine and aerospace area. Acoustic waves are easy to be transmitted through the outer shell to the interior especially at low frequencies, thus directly being scattered by the inner shell and the rings in water between double-layered shells. Therefore, the externally ring-stiffened cylindrical shell is investigated in this paper. An experiment was conducted that measured the acoustic scattering. A hybrid 2-D/3-D finite-element modelling technique is employed to numerically calculate the scattering characteristics. Good qualitative agreement is found between numerical calculations and experimental measurement. An approximate analytical expression is given explicitly to identify the Bragg wave trajectories in the frequency-angle spectrum. It also has been shown that the rings not only affect the dynamic response of shell and indirectly influence the exterior scattered field, but also become direct acoustic scatterers in water and increase the target cross section especially at oblique incidence.
Robust adaptive beamforming method for active sonar in single snapshot
Authors: Sun Xu , Li Ranwei
Published: June 2019

Forming narrow beams is a useful way for active sonar to anti-reverberation when it works in the shallow water. High-resolution adaptive beamforming with the performance of narrow beamwidths and low sidelobe levels is a better and more efficient method, particularly in the scenario where the installation space for sonar array is limited, such as hull-mounted sonar. Due to the short duration of target echo signal in the complex and varying acoustic channel, conventional adaptive beamforming methods are invalid. Therefore, this paper proposes a robust adaptive beamforming method for active sonar in single snapshot, also called the steered dominant mode rejection (STDMR). Firstly, STDMR steered the sample covariance matrix (STCM) based on wide-band focusing, which the needed number of snapshots is greatly reduced. Secondly, by partial eigendecomposition, the large eigenvalues of the STCM which are greater than the noise energy and their eigenvectors are used for dominant mode rejection (DMR). DMR is a typical eigenspace-based algorithm which has small computational load and fast convergence speed. Finally, modified with the methods of diagonal loading of 3-5dB over the noise energy and signal mismatch protection, improved the robustness of this method. Simulation and experimental data analysis shows that the STDMR method achieves narrow beams and low-level sidelobes in single snapshot. Hence, the STDMR beamformer is an appropriate implementation to use for active sonar detection systems.
Research on navigation for underwater unmanned vehicle based on dynamic gray filtering method
Authors: Wang Jinjin , Lin Tao , Fu Jin
Published: June 2019

According to the problem of large platform noise and external disturbance influence and the data may have outliers for UUV navigation, a dynamic grey filtering method based on fractional order operator is proposed. This method does not require prior knowledge and noise statistical properties of UUV system while establishing a dynamic grey model based on fractional operator according to navigation data. The deviation between the grey prediction value and the next navigation sample value is calculated and the data is fused according to the deviation to realize the real-time filtering. The simulation results show that the method is effective and feasible.
Three dimensional acoustic imaging technology of buried object detection
Authors: Cong Weihua , Zhou Lisheng
Published: June 2019

With the development of 21th century seabed imaging sonar technology, more and more attention is paid to buried object detection technology in the world. In this paper, a low frequency and high resolution three-dimensional acoustic imaging of buried object detection method and its application example are given. Compared with the traditional two-dimensional synthetic aperture imaging, the 3D imaging technology not only solves the problem of the aliasing of the seabed formation echo and the sea floor echo, being able to provide the target buried depth, but also the 3D imaging is more helpful to the image recognition. The 3D acoustic imaging method proposed by this paper has already become the development trend of buried object detection technology. We have noticed that, different from the three-dimensional visualization of the target in the water, the three-dimensional visualization of buried objects has a serious formation image occlusion problem. In addition, the three-dimensional imaging needs to be obtained centimeter-level resolution on three dimensions for better image recognition of small buried objects, in which azimuth resolution is the bottleneck.
Sonar image recognition based on fine-tuned convolutional neural network
Authors: Zhu Zhaotong , Hu Youfeng
Published: June 2019

To solve the problem of sonar image recognition, a sonar image recognition method based on fine-tuned Convolutional Neural Network (CNN) is proposed in this paper. With the development of deep learning, CNN shows impressive performance in image recognition. However, massive data is needed to train a CNN from beginning. Through fine-tuning pre-trained CNN can help us training CNN from relatively high starting points, based on those pre-trained CNNs, only few data is needed to retrain a CNN which focus on sonar image recognition. A scaled model experiment shows that based on the architecture of AlexNet, compared with the traditional learning method, the transfer learning method can achieve higher recognition accurate rate of 95.81% and less training time. Moreover, this paper also compared 6 pre-trained networks, among those networks, VGG16 can achieve the highest recognition rate of 99.48%.
Reconstruction of transient pressure and acceleration over a tire surface using the inverse time domain boundary element method
Authors: Zhang Yang , Bi Chuanxing , Zhang Xiaozheng , Zhang Yongbin , Xu Liang
Published: June 2019

The inverse time domain boundary element method (ITBEM) that is derived from the direct time domain boundary element method by eliminating the retarded time is able to reconstruct the transient pressure and flux on the surface of an arbitrarily shaped source by measuring the pressure on a hologram surface. In the present work, the ITBEM is applied to reconstruct the transient pressure and acceleration over the surface of a tire which is supported away from the ground in a semi-anechoic chamber. The tire is impacted by a rigid sphere to generate a transient sound field, and the measurement is controlled by a trigger which is connected to an acceleration sensor stuck on the surface of the tire. The pressure and acceleration on the surface of the tire are reconstructed from the holographic pressure measured by array microphones. By visualizing the pressure and acceleration with respect to the elapsed time, the wave propagation phenomenon of the pressure and acceleration on the surface of the tire is shown clearly. The comparison of the reconstructed surface acceleration to the measured one demonstrates the effectiveness of ITBEM for transient sound field reconstruction.
Ray-tracing-based time-domain wideband fractional delay beamforming for underwater acoustic positioning
Authors: Li Haipeng , Yuan Qingdong , Wu Yingyuan , Wang Xuebin
Published: June 2019

Underwater acoustic positioning systems are essential for underwater vehicles positioning and navigation. In this paper, a time-domain wideband fractional delay beamforming (WFDB) technique is proposed to improve underwater localization capability of planar arrays. In our method, digital delay lines are combined with adaptive-finite-impulse-response filters to achieve high accuracy beamforming results and reduce the design burden of the WFDB systems. Further, the beamforming results are used in the ray-tracing method to eliminate curvature effect of sound rays caused by the inhomogeneity of water, and therefore improving the computation accuracy of target position. We further develop a hexagonal planar array of 30 elements to verify the WFDB method in an indoor experimental pool. The experimental results demonstrate that the proposed method could successfully mitigate the ray bending problem and accurately estimate the position of targets in low SNR condition.
Finite element analysis of double resonance bender disk low frequency transducer
Authors: Lu Wei , Lan Yu , Zhou Tianfang
Published: June 2019

A bender disk transducer can generate low-frequency sound in a small size and light weight. But traditional bender disk transducer only works at single frequency by using first order bending mode and emits moderate levels of power. In this work, a double resonance bander disk low frequency transducer is investigated by using finite element model. The double resonance bender disk transducer consists of two segmented 3-3 mode piezoelectric ceramic disk on the both side of hollow metal disc, which could generate larger displacement in order to increase power radiation. A simple elastic mass system placed inside the hollow metal disc is introduced in the system to produce other lower resonance modes. Through the FEM calculations, it is found that the transmitting voltage response (TVR) of bender disk transducer could enhance 4dB in the first order bending mode resonance frequency, which is compared with traditional bender disk transducer with the same size. The TVR of lower resonance mode which is produced by additional central simple support elastic mass system in segmented bender disk transducer is more than 130dB. Through the optimization of finite element simulation, a double resonance bender disk transducer is designed, and its resonance frequency is 600Hz and 1kHz, respectively. The value of TVR is 130dB and 134dB corresponding to two resonance frequency. The double resonance bender disk transducer is compact dimension, low weight and it is a high performance low frequency transducer.
Weakly nonlinear oscillations of gas column driven by self-sustained sources
Authors: Hruška Viktor , Bednarřík Michal , Červenka Milan
Published: June 2019

Self-sustained sources coupled to some sort of resonator have drawn attention recently as a subject of nonlinear dynamics with many practical applications as well as interesting mathematical problems from the chaos theory and the theory of synchronizations. In order to mimic the self-sustainability arising from physical background the van der Pol equation is commonly used as a model (e.g. vortex induced noise, flowstructure interactions, vocal folds motion etc.). In many cases the sound field inside the resonator is strong enough for weakly nonlinear formulation based on the Kuznetsov model equation to be employed. An array of sources governed by the inhomogeneous van der Pol equation coupled to the nonlinear acoustic wave equation is studied. The one dimensional constant cross-section open resonator with zero radiation impedance is assumed. The focus is on the main features such as mode-locking, harmonics generation and build-up from infinitesimal fluctuations.
Improved proportionate FONLMS algorithm based direct adaptive Turbo equalization for MIMO underwater acoustic communications
Authors: Yang Zhuangchun , Liang Tianyi , Deng Zhourong , Zhang Youwen
Published: June 2019

In this paper, a novel normalized least mean squares (NLMS) algorithm that jointly updates the efficient of the linear equalizer and soft interference canceller (SIC) in an adaptive turbo equalizer for multiple-input multiple-output (MIMO) underwater acoustic (UWA) communications. To exploit the sparsity of MIMO UWA channels and enhance the convergence speed of adaptive equalization, improved proportionate fast self-optimized NLMS algorithm (IPFONLMS), is proposed to well adapt to sparse channel with the similar complexity as improve proportionate NLMS (IPNLMS) algorithm. Then we extend the proposed algorithm to the adaptive turbo equalization for MIMO UWA communications. The performance of the proposed adaptive algorithm is evaluated by numerical results. Simulation results show that the improved data efficiency and bit error ratio (BER) performance of the proposed receiver is achieved over adaptive turbo equalizer based on the IPNLMS algorithm.
Strong coherent interference suppression based on second- order cone null steering beamforming
Authors: Sun Dajun , Jia Zixuan , Teng Tingting , Huang Cong
Published: June 2019

For active sonar systems, coherent interference, such as direct-path wave and strong multi-path, will shield the weak target echo signal, which is one of the main factors affecting the target detection performance. Null steering beamforming is an important signal processing method that suppresses strong interference. In this paper, the second-order cone programming (SOCP) method is used to perform null steering beamforming on the uniform linear array. Beam null is caused in the direction of interference to suppress strong coherent interference in the active sonar system during detection. However, there are two limitations that can causes decline of the algorithm performance. A norm-control method is proposed to limit the response near the end-fire direction of linear array, and an array manifold compensation method is introduced to solve the array manifold mismatch. Simulated and experimental data was used to evaluate the performance and verify the feasibility of the methods.
Performance analysis of direct-sequence spread-spectrum underwater acoustic communications based on at-sea data
Authors: Du Pengyu , Wang Lujun , Zhang Hongtao , Xie Zhe
Published: June 2019

Direct sequence spread spectrum (DSSS) signal uses phase coherent signals where the information symbols are multiplied with a code sequence, commonly known as chips. The signals are processed at the receiver using the code sequence as a matched filter to extract the information symbols. Taking advantage of the spread processing gain derived from the matched filter, communications can be carried out at low signal levels, which is the preferred method for high quality underwater acoustic (UWA) communication and remote UWA communication. However, in practical applications, DSSS UWA communication will face lots of interferences including multipath interference, Doppler compression interference and phase fluctuation interference, which will seriously affect the performance of DSSS. This paper first analyzes the interferences that DSSS faces in practical applications based on multiple actual received data collected in different water areas. By calculating the gain of the matched filter loss, one can find that influence of phase fluctuation interference has the most serious impact on DSSS. Secondly, the corresponding receiver processing algorithms are given for these interferences, including the differential energy detector and Doppler estimation method. The performance of differential energy detector under the above interferences is analyzed, which shows that the differential energy detector is insensitive to slow phase fluctuation interference and multipath interference and the differential energy detector combined with Doppler compensation can work well based on moving at-sea data. Finally, the parameter design of DSSS system in practical application is discussed and parameter design of DSSS UWA communication system should comprehensively consider the Doppler compression interference and phase fluctuation interference.
Nonlinear dimensionality reduction for the acoustic field measured by a linear sensor array
Authors: Zhang Xinyao , Wang Pengyu , Wang Ning
Published: June 2019

Dimensionality reduction is one of the central problems in machine learning and pattern recognition, which aims to develop a compact representation for complex data from high-dimensional observations. Here, we apply a nonlinear manifold learning algorithm, called local tangent space alignment (LTSA) algorithm, to high-dimensional acoustic observations and achieve nonlinear dimensionality reduction for the acoustic field measured by a linear senor array. By dimensionality reduction, the underlying physical degrees of freedom of acoustic field, such as the variations of sound source location and sound speed profiles, can be discovered. Two simulations are presented to verify the validity of the approach.
Research on reverberation characteristics analysis and suppression methods for active continuous detection
Authors: Chen Tuo , Ma Qiming , Zhou Zheyuan , Lu He
Published: June 2019

Compared with the traditional active detection with monopulse periodic emission mode, active continuous detection has the advantages of large emission duty ratio and continuous acquisition of process information. It can effectively overcome the disadvantages of high false alarm probability, poor environment adaptation ability and low detection efficiency in traditional active detection, so then improving the system detection ability. But active continuous detection is also facing more serious reverberation. In order to further improve capacity, the adaptable reverberation characteristics and detection methods are carried out in this paper. On the basis of theoretical modelling, the relationship between the characteristics of the active continuous detection reverberation and the signal form, the hydrological environment and the emission power are studied. The time frequency characteristics of reverberation and the attenuation law with distance of reverberation are mastered. A reverberation suppression method based on adaptive beamforming of sub-band steered minimum variance algorithm (SSMV) is studied for active continuous detection. Considering signal bandwidth and fast convergence, etc. The relationship between sub-array partition and reverberation suppression ability is analyzed. The validity of reverberation characteristic analysis is verified by simulation, the performance of the method of reverberation suppression is verified by sea trial data processing.
Vibration behaviour of a bio-composite sandwich with auxetic core
Authors: Essassi Khawla , Rebiere Jean-Luc , El Mahi Abderrahim , Toure Mahamane , Ben Souf Mohamed amine , Bouguecha Anas , Haddar Mohamed
Published: June 2019

This paper describes the flexural vibration and damping performances of an eco-composite sandwich structure with re-entrant honeycomb core. The main objective of this study is to analyse the effect of flax fibre reinforcement composite and the densities of the auxetic core on the dynamic properties of the sandwich structures. The damping properties and the sandwich stiffness are determined in bending beams for different free lengths in a clamped-free configuration. Firstly, the dynamic properties of the skins were investigated in order to develop the evolution of mechanical properties as well as damping coefficient for each material. Then, the same characterization was tested on the sandwich structures with different core densities. The results obtained showed that both core densities and flax fibre as reinforcement plays a major role on the dynamic properties of the sandwich composite structures.
The influence of impedance mismatch of the medium with gradient change of impedance on acoustic characteristics
Authors: Hu Bo , Wang Moran , Du Yimei
Published: June 2019

Medium with gradient change of acoustic impedance is a new type acoustic structure. It is composed of several materials and has a continuous gradient composition and structure whose specific acoustic impedance varies smoothly across the layer. It has been used in various practical situations such as acoustic rectifiers, medical devices, weakening vibration and reducing noise. The purpose of this paper is to investigate the effect of boundary impedance mismatch on acoustic characteristics of gradient impedance media. The propagation mechanism of acoustic waves in medium with gradient change of specific acoustic impedance was calculated by transfer matrix method. By setting the different ratios of the acoustic impedance at interfaces of matching layer, the relationship between specific acoustic impedance mismatch and acoustic characteristics are derived and the corresponding conclusions are drawn. These conclusions provide an idea for the preparation of relevant medium.
Model approximation for sound transmission from underwater structures in high-frequency range
Authors: Zhang Rui , Yang Desen , Shi Shengguo , Yang Boquan
Published: June 2019

Sound-insulation model provides a straightforward way to describe sound transmission behaviours of the thin-walled structures in engineering applications. The sound transmission characteristics depend on the parameters of incident wave, such as incident wave amplitude and incident angles. However, this model is limited when the sound source is located in an enclosed space (e.g., noise source in underwater cabins), because it is difficult to obtain incident angles especially in the high-frequency range. In this paper, we develop a simply analytical model that can effectively study the sound transmission from an enclosed shell with internal acoustic excitation. In order to extend the application of the sound-insulation model to a submerged shell, the structural vibration equation is firstly simplified to the plate vibration equation. Then, the sound pressure near the inner surface of the shell is decomposed into an expansion of orthogonal cavity eigenmodes, and each cavity mode is replaced by two pairs of incident plane waves. Finally, the acoustic transmission loss can be obtained by substituting the parameters of incident waves into the sound-insulation model. Numerical results show that the sound transmission for the fundamental cavity mode (0, 0, 0) can be explained by the normal incidence in the sound-insulation model, while every other modes corresponds to a group of oblique incident plane waves whose incident angles decrease monotonically with the increase of frequency. In addition, it can be observed that the total reflection phenomenon in the sound-insulation model is consistent with the low radiation efficiency of the high order modes in the shell model.
Temperature feedback algorithm for efficient electron beam heating of titanium melt
Authors: Tsybrii Yurii , Grabovskiy Heorhiy
Published: June 2019

High-quality electron beam melting of titanium requires a uniform heating of the melt in the intermediate container of the electron beam unit and an efficient distribution of the power of the electron beam guns. In this study, we investigated the efficiency of different algorithms to control the electron beam trajectory. Three-dimensional transient heat transfer in the intermediate container was simulated using finite element method. It was shown that the standard algorithm, with a zigzag trajectory provides uniform heating of the melt in the absence of unmelted furnace charge. A temperature feedback algorithm allows heating the melt within the required temperature range in the presence of the furnace charge, but it doesn’t provide temperature distribution uniformity. Based on the mentioned algorithms, a combined algorithm was proposed which allows efficient heating of the melt regardless of the presence or absence of the furnace charge. The implementation of the combined algorithm into the technological process allows a substantial increase in the productivity of titanium melting.
Coaches’ interpersonal emotion regulation and the coach-athlete relationship
Authors: Braun Courtney , Tamminen Katherine A.
Published: June 2019

Researchers have examined the impact of coaches’ emotional expressions and emotional intelligence on athlete outcomes (Allan, V., & Côté, J. (2016). A cross-sectional analysis of coaches’ observed emotion-behavior profiles and adolescent athletes’ self-reported developmental outcomes.Journal of Applied Sport Psychology,28, 321–337; Thelwell, R.C., Lane, A.M., Weston, N.J., & Greenlees, I.A. (2008). Examining relationships between emotional intelligence and coaching efficacy.International Journal of Sport and Exercise Psychology,6, 224–235; van Kleef, G.A., Cheshin, A., Koning, L.F., & Wolf, S.A. (2018). Emotional games: How coaches’ emotional expressions shape players’ emotions, inferences, and team performance.Psychology of Sport & Exercise). However, there is little research examining coaches’ use of specific strategies to regulate their athletes’ emotions. The purpose of the present study was to explore the strategies coaches used to try and regulate their athletes’ emotions, and to explore the relationship and contextual factors influencing coaches’ IER strategy use. A longitudinal multiple case study approach was used (Stake, R.E. (2006). Multiple case study analysis. New York: The Guilford Press) with five cases, each consisting of one male coach and two individual varsity sport athletes (N = 15). Participants completed individual interviews, a two-week audio diary period, and a follow-up interview. Data were inductively and deductively analyzed and a conceptual model was developed outlining athletes’ emotions and emotion regulation, coaches’ IER, the coach-athlete relationship, and contextual factors. Participants described a bidirectional association between the coach-athlete relationship and coaches’ IER. A number of factors influenced athletes’ and coaches’ use of emotion regulation strategies and contributed to the quality of the coach-athlete relationship. The IER strategies that coaches used may reflect instrumental, performance-related motives, and coaches’ IER efforts may also contribute to coaches’ emotional labour.
Therapiesteuerung der COPD durch eosinophile Granulozyten?
Authors: Magnussen Helgo
Published: June 2019

Symptomatic patients with COPD reporting about repeated exacerbations in their history (group D according to GOLD recommendations) are treated with dual bronchodilation (LAMA/LABA) with potential benefits from additional ICS. Eosinophils in peripheral blood are considered as potential biomarkers to predict exacerbations. > 300 cells/µL or 4 % of eosinophils in peripheral blood are recommended to treat the patients with additional ICS. In clinical practice, about 10 – 15 % of patients with COPD are classified as group D according to GOLD. < 20 % have increased eosinophils in peripheral blood. Thus, ICS therapy should be restricted to a minority of patients with COPD
Hämorrhagisch-ulzeröser Verlauf einer eosinophilen Gastritis bei einem 79 Jahre alten Mann
Authors: Wennmann Merlin , Trenn Guido
Published: June 2019

Die eosinophile gastrointestinale Erkrankung (EGID) ist ein seltenes Krankheitsbild weitgehend unklarer Ätiologie. Wir beschreiben im Folgenden den Fall eines 79-jährigen Patienten mit der Erstdiagnose einer eosinophilen Gastritis mit hämorrhagisch-ulzerösem Verlauf und einer raschen Rekurrenz der Erkrankung nach Absetzen der medikamentösen Therapie.

Anamnese und klinischer Befund Der Patient gab an, seit mehreren Tagen Teerstuhl abzuführen. Zum Aufnahmezeitpunkt war der Patient beschwerdefrei. Die bestehende Medikation wurde in letzter Zeit nicht verändert.

Untersuchungen und Diagnose Gastroskopisch, endosonografisch und im CT fand sich ein malignitätsverdächtiger Tumor im Corpus ventriculi. Erst die histopathologische Untersuchung lieferte die korrekte Diagnose.

Therapie und Verlauf Der Patient wurde mit Prednisolon und PPI behandelt. Hierunter kam es zu einer Regredienz des Befundes und einer klinischen Vollremission. Ein Auslassversuch führte kurze Zeit später zu einem fulminanten Rezidiv. Nach Wiederaufnahme der medikamentösen Therapie war das erneut nachgewiesene gastrale Ulkus rasch rückläufig.

Folgerung Die EGID ist vom klinischen Erscheinungsbild her kaum zu identifizieren. Zur Diagnosestellung bedarf es einer histopathologischen Begutachtung. In der Behandlung spielen vor allem orale Glukokortikoide eine Rolle. Es sind sowohl Einzelepisoden als auch chronisch-rezidivierende Verläufe beobachtet worden. Die zur Therapie eingesetzten Medikamente sollten daher nur vorsichtig und unter regelmäßiger Befundkontrolle ausgeschlichen werden.
Pneumologische Frührehabilitation nach Langzeitbeatmung
Authors: Dellweg Dominic , Siemon Karsten , Höhn Ekkehard , Barchfeld Thomas , Köhler Dieter
Published: June 2019

Einleitung Unter Frührehabilitation versteht man eine frühzeitig bei- oder nach akuter Erkrankung einsetzende, rehabilitationsmedizinische Behandlung die im § 39SGB V verankert ist. Ziel dieser Untersuchung ist es, die Ergebnisqualität der pneumologischen Frührehabilitation zu untersuchen und darzustellen.

Methoden Prospektive Erhebung von funktionellen Parametern, Beatmungsstatus und Entlass-Disposition in einer spezialisierten Abteilung für pneumologische Frührehabilitation über den Zeitraum von einem Jahr.

Ergebnisse Von den 190 Patienten waren 179 (94,2 %) zuvor invasiv beatmet. Während einer Behandlungsdauer von 39 ± 17 Tagen stieg der FAM-Index von 84,4 ± 19,8 auf 118,5 ± 23,3 (Ci 30,9 – 37,3, Cohen’s d 1,58; p < 0,001), der Barthel-Index von 30,5 ± 13,8 auf 58,3 ± 16,2 (Ci 25,4 – 33,8, Cohen’s d 1,4; p < 0,001) und die Wegstrecke von 12,9 ± 40,1 m auf 131,4 ± 85,2 m (Ci 105,6 – 131,4 m, Cohen’s d 1,78; p < 0,001). Die Patienten wurden weniger häufig in eine weitere Anschlussheilbehandlung verlegt, wenn sie beatmet waren.

Diskussion Patienten in der pneumologischen Frührehabilitation sind bei Aufnahme schwer kompromittiert, es lässt sich aber eine sehr gute Ergebnisqualität erzielen, die unabhängig davon zu sein scheint, ob der Patient eigenständig atmet oder mittels nicht-invasiver oder invasiver Beatmung versorgt wird. Die weitere Disposition dieser Patienten ist vor allem dann schwierig, wenn eine Beatmung vorliegt.
Schock – eine Übersicht für die klinische Praxis
Authors: Hempel Dorothea , Michels Guido
Published: June 2019

Diagnosing and managing patients in shock is a challenge for the treating clinicians in acute medicine. Early diagnosis and treatment are crucial. Mortality of septic shock is between 40 % and 60 %, and that of the cardiogenic shock about 40 %. This article provides an overview of diagnostic approaches to the patient in shock, different aetiologies and treatment strategies, and it guides the clinician through the management from first contact until definite treatment.
Owning a Dog as a Determinant of Physical
Activity and Metabolic Control in Patients With
Type 1 and Type 2 Diabetes
Mellitus
Authors: Riske Julia , Janert Martin , Kahle-Stephan Melanie , Nauck Michael A.
Published: June 2019

Background/aims Physical activity is
recommended for patients with type 1 (T1D) and
type 2 diabetes (T2D). We wanted to assess whether
owning a dog influences duration or intensity of
physical activity and metabolic control of
diabetes mellitus.

Patients and methods 143 patients with T1D
(age 50±16 y.; BMI 25.7±4.5 kg/m2,
HbA1c 8.6±1.6%) and 303 with T2D (age
63±11 y., BMI 33.7±7.3 kg/m2,
HbA1c 9.0±1.6%, 232 [76.6%]
insulin-treated, 89±61 IU/d), respectively,
participated. A standardized questionnaire
assessed diabetes history and treatment, details
regarding time spent (per week) and intensity
(MET, metabolic equivalent of task) of physical
activity (“walking the dog” and other activities),
anthropometric (BMI) and laboratory measures.

Results 31.5% of T1D 23.1% of T2D patients
were dog owners. Dog owners with T1D and T2D
diabetes spent 19.0±3.3 and 19.8±2.6
MET.h per week walking the dog, which
represented 61.3±5.7 and 62.9±4.9% of their total
physical activity. Participants not owning a dog
compensated by performing significantly more other
activities. Taken together, total physical
activity was similar in dog owners with T1D
(p=0.80), but higher in dog owners with T2D
(30.1±2.8 vs. 18.6±1.4 MET.h per week
in those not owning a dog; p=0.0001).
Body-mass-index or HbA1c were not
significantly different in either patients with
T1D or T2D either owning a dog or not.

Conclusions Owning a dog motivates to a
significant amount of physical activity, but this
was fully compensated for by other forms of
physical activity in (younger) patients with T1D.
Even the higher physical activity in dog owners
with T2D did not result in improved glycaemic or
body weight control.
Glukosemessverfahren und deren Einfluss auf die Diabetologie
Authors: Thomas Andreas , Siegmund Thorsten , Kolassa Ralf
Published: June 2019

Nach der Nutzung des Insulins für die Diabetesbehandlung gab es kaum einen weitreichenderen therapeutischen Fortschritt als die Einführung verschiedener Methoden der Glukosemessung zur unmittelbaren Selbstkontrolle der Patienten. Dadurch eröffnete sich die Möglichkeit, die Therapie zu steuern und mit den unterschiedlichen Anforderungen des Alltags abzustimmen. Schlussendlich eröffnete das den Patienten ein Diabetesmanagement, welches im täglichen Leben weniger Einschränkungen durch die Therapie bedeutet. Mit jedem weiteren Entwicklungsschritt der Glukoseselbstmessung erhöhte sich deren Einfluss. Weil mit dem kontinuierlichen Glukosemonitoring (CGM) eine vollständige Abbildung des Glukoseverlaufs gegeben ist, lassen sich diese Daten auch innerhalb von Algorithmen zur Therapiesteuerung nutzen. Einerseits betrifft das die automatisierte Steuerung der Insulinabgabe von Insulinpumpen, andererseits die Empfehlung von therapeutischen Maßnahmen nach Analyse der Glukosedaten auf Großcomputern mithilfe von Therapieentscheidungsalgorithmen. Waren und sind die verschiedenen Glukosemessverfahren bereits Werkzeuge für die Therapieunterstützung, so ist CGM eine Voraussetzung für die Therapiesteuerung. Auf dieser Ebene ist eine ständige Weiterentwicklung zu beobachten.
Schlüsseltechnologien für zukünftige Glukosemessverfahren
Authors: Thomas Andreas , Ramírez Araceli , Zehe Alfred
Published: June 2019

Die Herstellung von Glukosesensoren für das kontinuierliche Glukosemonitoring (CGM) ist aufwendig, wodurch die Messung nicht preiswert ist. Der Einsatz moderner Technologien, insbesondere der Zugang zur Mikroelektroniktechnologie könnte zu deutlich kostengünstigeren integrierten Glukosemesschips führen. Darüber hinaus kann die Anwendung der Nanotechnologie, einer aufkommenden Schlüsseltechnologie, zukünftig hochsensible und selektiv messende Glukosesensoren hervorbringen, die sich mit beliebigen anderen Sensoren für die Messung von Körperzuständen kombinieren lassen. Das dürfte auch nicht-invasive Messungen unter alltäglichen Bedingungen realistisch erscheinen lassen.