bluuebunny/crossref_metadata_2025 huggingface dataset:
Longitudinal Study of Expressive Language and Speech of Twins at 3 and 5 Years: Outgrowing a Twinning Effect
Authors: Culloty Amy M. , O'Toole Ciara , Gibbon Fiona E.
Published: June 2019

Purpose

This study examines the expressive language and speech of twins, relative to singletons, at 3 and 5 years, with the aim of determining if a twinning effect occurs during this developmental period. The possibility of twins outgrowing a twinning effect was investigated.

Method

A weighted population-based sample of 185 twins and 1,309 closely spaced singletons who participated in the Growing Up in Ireland study was analyzed. Their development was compared using a standardized expressive vocabulary assessment and parent interview at 3 and 5 years as well as teacher reports at 5 years. Causal steps mediation analyses were subsequently conducted to determine if gestation and birth weight mediated twin–singleton differences in expressive vocabulary development.

Results

Twins' expressive vocabulary scores were slightly lower than those of singletons at 3 years, but there was no significant difference at 5 years. More parents of twins reported “a little” concern about their child's expressive language and speech skills at 3 years, although there was no significant twin–singleton difference 2 years later. Teachers' ratings of twins' and singletons' expressive language and speech skills at 5 years were comparable. Shorter gestations and lower birth weights mediated twins' lower expressive vocabulary scores at 3 years.

Conclusions

A very small twinning effect on expressive vocabulary development exists at 3 years and is outgrown by 5 years. Twins born after shorter gestations or at a lower birth weight are at an increased risk of having less developed expressive vocabulary skills at 3 years.
Accent Intelligibility Differences in Noise Across Native and Nonnative Accents: Effects of Talker–Listener Pairing at Acoustic–Phonetic and Lexical Levels
Authors: Stringer Louise , Iverson Paul
Published: June 2019

Purpose

The intelligibility of an accent strongly depends on the specific talker–listener pairing. To explore the causes of this phenomenon, we investigated the relationship between acoustic–phonetic similarity and accent intelligibility across native (1st language) and nonnative (2nd language) talker–listener pairings. We also used online measures to observe processing differences in quiet.

Method

English (n= 16) and Spanish (n= 16) listeners heard Standard Southern British English, Glaswegian English, and Spanish-accented English in a speech recognition task (in quiet and noise) and an electroencephalogram task (quiet only) designed to assess phonological and lexical processing. Stimuli were drawn from the nonnative speech recognition sentences (Stringer & Iverson, 2019). The acoustic–phonetic similarity between listeners' accents and the 3 accents was calculated using the ACCDIST metric (Huckvale, 2004,2007).

Results

Talker–listener pairing had a clear influence on accent intelligibility. This was linked to the phonetic similarity of the talkers and the listeners, but similarity could not account for all findings. The influence of talker–listener pairing on lexical processing was less clear; the N400 effect was mostly robust to accent mismatches, with some relationship to intelligibility.

Conclusion

These findings suggest that the influence of talker–listener pairing on intelligibility may be partly attributable to accent similarity in addition to accent familiarity. Online measures also show that differences in talker–listener accents can disrupt processing in quiet even where accents are highly intelligible.
Pharyngeal Manometry in Pediatric Dysphagia Assessment
Authors: Ferris Lara , Omari Taher
Published: June 2019

Purpose

Reliable measures to capture swallowing pathophysiology and outcomes from therapeutic interventions are needed in the pediatric setting. Therefore, this review presents the current best evidence for manometry investigation and its application in pediatric dysphagia. For oropharyngeal dysphagia assessment, videofluoroscopic swallow study is considered the gold standard, and fiberoptic endoscopic examination of swallowing is also employed in some settings. In clinical practice, both tests mostly rely on qualitative interpretation of image data and have variable reliability to detect pathophysiology.

Conclusion

Acknowledging that swallowing is a pressure-driven event, the role of manometry is now being considered as an objective, nonradiological technique that can be performed as an adjunct to other clinical swallow evaluations. The latest high-resolution manometry catheter technologies are miniaturized and simple to use, enhancing their potential application in pediatric clinical and research contexts.
Novel semi‐analytical method for mutual inductance calculation of the thin spiral disk coils
Authors: Yıldırız Emin , Kemer Salih Burak
Published: June 2019

Accurate and fast calculation of the self and mutual inductance of coils is an important factor in system design and optimization for many applications. The methods of calculation mutual inductance between two spiral disk coils include elliptic integral solutions and coefficients in literature. In this study, a new semi‐analytical method is proposed to calculate the mutual inductance between two thin disk coils without any coefficient and complex integral solutions. For this purpose, the circular winding is treated as polygonal winding with multiple edges. Unlike Grover's average diameter approach, the gaps between the turns of the coils and the diameter of the wire are included in the calculation. To observe the reliability of the method developed here, the mutual inductance between identical disk coils with an inner diameter of 10 and 20 cm were calculated using both methods. To confirm the accuracy of the proposed method, the experimental results are compared with two methods using the same coils. It is observed that the new method gives acceptable results (maximum error of 2.83%) especially at the distances equals to the inner radius. Consequently; this method is useful for the design of loosely coupled systems, such as wireless power transfer and pressure sensors.
Experimental electrical characterisation of carbon fibre composites for use in future aircraft applications
Authors: Khan Jameel B. , Smith Alexander C. , Tuohy Paul M. , Gresil Matthieu , Soutis Constantinos , Lambourne Alexis
Published: June 2019

This study presents experimental testing of samples from two uni‐directional carbon fibre composite (CFC) manufactured panels to determine the factors that influence the electrical properties of CFCs and to also determine the temperature coefficient of resistance. The CFC panels were manufactured by two different techniques to compare the impact of the manufacturing process on the electrical properties. Various electrical conductivity measurement methods were evaluated to determine the most consistent and accurate technique. The influence of sample geometry on the measured electrical conductivity was also investigated. Thermal imaging was used to image resistive losses and illustrate the current paths through the fibres within the CFC test samples. Finally, the effects of increasing temperature on the CFC samples are presented, illustrating that CFCs have a negative temperature coefficient.
Evaluating flexibility values for congestion management in distribution networks within Dutch pilots
Authors: Fonteijn Rik , van Amstel Marieke , Nguyen Phuong , Morren Johan , Maarten Bonnema Gerrit , Slootweg Han
Published: June 2019

Decentralisation of electricity generation, and electrification of heating and transportation pose challenges for the distribution networks, such as possible network congestion. Network operators investigate alternatives for reinforcements. Flexibility through demand response (DR) is one of these alternatives. Four theoretical possibilities for flexibility as a solution for congestion management are presented, in relation to four pilot projects on congestion management in the Netherlands. This article evaluates these four pilot projects based on six evaluation criteria. The strengths and weaknesses of all pilots are addressed, and the results of the pilot projects are discussed.
Voltage stability index and APFC for performance improvement of modern power systems with intense renewables
Authors: Singh Pradeep , Tiwari Rajive , Shah Mukesh Kumar , Niazi Khaleequr Rahman , Meena Nand Kishor , Ratra Saurabh
Published: June 2019

In this study, a newly developed amalgam power flow controller (APFC) is used for better controllability and voltage stability enhancement of modern power system with deep renewable penetration. A new voltage stability index is proposed to determine the potential site of APFC and then Grey Wolf optimisation based on fuzzy logic is adopted to determine the optimal parameter settings of the APFC. A quarter cosine and exponential fuzzy membership function have been used to find out membership value of diverse objectives. The multi‐objective problem is formulated considering three different objectives of conflicting nature. The proposed optimisation framework is implemented on an IEEE benchmark system of 30 buses for different cases. The comparison of simulation results reveals the effectiveness of the proposed model.
Study on the best calculation scheme of equivalent evaporation duct feature
Authors: Liang Xiang , Tian Bin , Lv Xinshuai , Yan Jiawei
Published: June 2019

In view of the lack of applicability of the existing equivalent evaporation duct feature calculation scheme in China's sea area and the requirement of the evaporation duct model test, this study used the actual sounding data in China's coastal areas and studied the applicability of the three computational schemes proposed by J.F. Howell, S.P. Oncley, and G.J. Steeneveld in different sea areas and different seasons by comparing the error and standard deviation. The applicability of the sea area shows that the best calculation scheme for the equivalent evaporating duct feature in the South China Sea is the scheme proposed by G.J. Steeneveld et al., while the optimal calculation method for the East China Sea is the scheme proposed by S.P. Oncley et al.; the seasonal applicability shows that the scheme proposed by G.J. Steeneveld et al. has the best‐fitting results in the spring, while in the summer and winter, the scheme proposed by S.P. Oncley et al. fits best. These results provide a theoretical basis for the follow‐up study.
Reduced‐dimension space‐time adaptive processing for airborne radar with co‐prime array
Authors: Wang Xiaoye , Yang Zhaocheng , Huang Jianjun
Published: June 2019

Space‐time adaptive processing (STAP) for airborne radar with co‐prime arrays is shown to have excellent superiority compared to traditional STAP with uniform linear array radar. However, high arithmetic computational complexity and large amount of training data are required in this approach. This motivates the authors to present a new approach which is relatively low computational load and fast convergence with satisfactory performance. Specifically, a reduced‐dimension transformation in Doppler domain is incorporated into the existing approach. The reduced‐dimension interference covariance matrix and target steering vector are then achieved by performing the reduced‐dimension process, and hence two reduced‐dimension STAP filters are designed using the derived interference covariance matrix and target‐steering vector. Numerical simulations are carried out to reveal the superiority of the proposed approach.
Fast mesh forming for distributed digital array radar
Authors: Guanghu Jin , Tao Chen , Zhen Dong
Published: June 2019

Distributed digital array radar (DDAR) can operate in multiple modes and perform multiple functions. Compared with traditional phased array radars, the performance advantages of DDAR are obvious in many aspects. One of them is that DDAR can form space mesh in a wide scope. This article proposes a new fast mesh forming method. Unlike traditional multiple beam forming, the authors’ algorithm can form a mesh along range and azimuth. First, the range profile is obtained based on fast Fourier transform. Second, the mesh forming is divided into several steps that are accomplished in polar formatted plane. Finally, the polar formatted result is transformed into Cartesian coordinates. The authors tested the method using RADBASE data, which shows that the authors’ algorithm has good performance.
Fast algorithm for moving target localisation using FDA‐MIMO radar
Authors: Xu Jian , Wang Wen‐Qin , Cui Can , Huang Bang
Published: June 2019

Target localisation using frequency diverse array (FDA) has drawn much attention owing to the additional degree of freedom in the range dimension. However, the Doppler effect was often ignored in previous FDA works because of the stationary target assumption, and in contrast, even stationary target localisation could be of quite a high computational complexity. In this study, a method is proposed that can jointly estimate range, angle, and Doppler for FDA multiple‐input‐multiple‐output radar with low computational complexity. First, Doppler is estimated independently by utilising unstructured maximum likelihood method. Next, traditional two‐dimensional (2D) MUSIC is divided into multiple one‐dimensional (1D) MUSIC to estimate the angle. Then substituting the estimated angle into the former 2D MUSIC results in a 1D searching over range dimension to get the range estimation. The advantage of the proposed method was verified by simulation results.
GIADA microbalance measurements on board Rosetta: submicrometer- to micrometer-sized dust particle flux in the coma of comet 67P/Churyumov-Gerasimenko
Authors: Della Corte V. , Rotundi A. , Zakharov V. , Ivanovski S. , Palumbo P. , Fulle M. , Longobardo A. , Dionnet Z. , Liuzzi V. , Salatti M.
Published: June 2019

Context. From August 2014 to September 2016, Rosetta escorted comet 67P/Churyumov-Gerasimenko (67P) during its journey around the Sun. One of the aims of Rosetta was to characterize cometary activity and the consequent formation of dust flux structures in cometary comae.

Aims. We characterize and quantify the submicrometer- to micrometer-sized dust flux that may be shaped in privileged directions within the coma of 67P inbound to and outbound from perihelion.

Methods. The in situ dust-measuring instrument GIADA, part of the Rosetta/ESA payload, consisted of three subsystems, one of which was the Micro Balance Subsystem (MBS), composed of five quartz crystal microbalances. From May 2014 to September 2016, MBS measured the submicrometer- to micrometer-sized deposited dust mass every 5 min.

Results. We characterized the submicrometer- to micrometer-sized dust mass flux in the coma of 67P. The anti-sunward and the radial direction are preferred, and the flux is higher in the anti-sunward direction. The measured cumulative dust mass in the anti-sunward direction is 2.38 ± 0.04 × 10−7 kg, and in the radial direction, it is 1.18 ± 0.02 × 10−7 kg. We explain the anti-sunward dust flux as the effect of nonuniform gas emission between the night- and dayside of the nucleus, which acts in combination with the solar radiation pressure. We compared the cumulated dust mass of particles ≤5 μm with particles ≥100 μm. The retrieved ratio of ≈2% implies a differential size distribution index of ≈−3.0, which confirms that particles of size ≥0.1 mm dominate the dust coma cross-section of 67P during the entire orbit.

Conclusions. Submicrometer- to micrometer-sized dust mass flux measurements were made for the first time from the arising of cometary activity until its extinction. They indicate that these particles do not provide a substantial optical scattering in the coma of 67P with respect to the scattering caused by millimeter-sized particles. In addition, MBS data reveal that the measured dust flux is highly anisotropic: anti-sunward plus radial.
Experimental Study of a Boundary Layer on a Heated Flat Plate
Authors: Antoš Pavel , Kuznetsov Sergei
Published: June 2019

Boundary layer on a uniformly heated flat plate was studied experimentally. Both, the velocity boundary layer and the temperature boundary layer, was investigated by means of hot-wire anemometry. A probe with parallel wires was used for velocity-temperature measurement. Experiment was performed in the closed-circuit wind tunnel with several levels of heat flux at the wall. The wall temperature was set up in the interval from 20 ºC to 200 ºC.
Investigation of the membrane regeneration methods by flow visualization
Authors: Bílek Petr , Brich Josef
Published: June 2019

This paper deals with an investigation of regeneration methods on a flat sheet membrane by flow visualization of the inlet side of a filter. The regeneration significantly increases performance of the membranes, extends its lifetime and saves resources. The regeneration process prevents depositing of particles on the filter surface and forming a filtration cake as well as reopens clogged pores in the filter structure. The visualization of flow helps deeper investigation of different regeneration methods because it brings a new view on the filtration/regeneration process on a thin laser sheet whilst it is recorded by a digital camera. The result is, besides the overall view, just the local concentration of the particles, which is determined by image analysis of the recorded pictures from the camera. The amount of the deposited particles on the filter is compared to the hydrodynamic data and the effect of the tangential flow and bubbling intensity parameters is investigated in the article. The tests are carried out on a low volume laboratory filtration setup - LSD 115 with a new optic filtration channel.
Simulation research of the temperature distribution during face milling
Authors: Blasiak Malgorzata , Nowakowski Lukasz
Published: June 2019

The paper presents the results of numerical calculations showing the temperature distribution of the workpiece (copper) during the face milling process. The ANSYS program was used for simulation studies. The calculations were carried out for two different cutting speeds, examining their influence on the temperature of the workpiece. The calculations constitute the basis for further research in order to determine the influence of variable temperature fields on the thermal expansion of the workpiece and to estimate the dimensional accuracy of the parts to be made during milling.
Space-time discontinuous Galerkin method for the numerical simulation of the compressible turbulent gas flow through the porous media
Authors: Česenek Jan
Published: June 2019

The article is concerned with the numerical simulation of the compressible turbulent gas flow through the porous media using space-time discontinuous Galerkin method.The mathematical model of flow is represented by the system of non-stationary Reynolds-Averaged Navier-Stokes (RANS) equations. The flow through the porous media is characterized by the loss of momentum. This RANS system is equipped with two-equation k-omega turbulence model. The discretization of these two systems is carried out separately by the space-time discontinuous Galerkin method. This method is based on the piecewise polynomial discontinuous approximation of the sought solution in space and in time. We present some numerical experiments to demonstrate the applicability of the method using own-developed code.
Experimental analysis of static and dynamic properties of the check valves
Authors: Dokoupil Pavel , Himr Daniel , Habán Vladimír
Published: June 2019

The check valves play an important role in safety and reliability of many technologies using liquid or gas flow. Check valves are elements of the hydraulic system enabling the one-way flow without a significant pressure loss and preventing the reverse flow. The ideal check valve should have an acceptable pressure loss and, when closed, there should be no undesirable dynamic phenomena like water hammer or slam. The static properties describe energy losses of the check valve, and the producers provide them as a standard. The static properties can be defined either in an experimental way or using the CFD analysis. The dynamic properties of the check valve express a relation between the maximum reverse velocity and water column deceleration. Unfortunately, the definition of dynamic properties can be obtained only experimentally, and for small pipe diameters. It is very demanding, time consuming and expensive to define the dynamic characteristic so it is why the producers do not offer it as a standard. The article deals with static and dynamic properties of different check valves with different closing principles. There was built a testing hydraulic circuit with the pipe diameter DN 100, that enables the simulation of check valve slam during the flow reversing. The attention was paid to the definition of flow deceleration, which is rather problematic and usually defined in a different way for each lab.
Simulation of parallel capacitance influence on the hydraulic system dynamics
Authors: Filip Dýrr , Lumír Hružík , Adam Bureček , Petr Brzezina
Published: June 2019

This paper covers with experimental measurement and mathematical simulation of parallel capacitance influence on pressure response for non-stationary flow. The hydraulic circuit for measuring required quantities, which are necessary to determine of parallel capacitance influence on the hydraulic system dynamics. A part of hydraulic system is a long pipe, in which the parallel capacitance created by hydraulic hose is connected. A non-stationary flow is caused by fast closing of the seat valve, which is situated at the end of long pipe. Mathematical model is realized and verified in Matlab SimScape Fluids software for this hydraulic system.
Signals features extraction in radioisotope liquid-gas flow measurements using wavelet analysis
Authors: Hanus Robert , Zych Marcin , Wilk Barbara , Jaszczur Marek , Świsulski Dariusz
Published: June 2019

Knowledge of the structure of a flow is significant for the proper conduct of a number of industrial processes. In this case, a description of a two-phase flow regimes is possible by use of the time-series analysis in time, frequency and state-space domain. In this article the Discrete Wavelet Transform (DWT) is applied for analysis of signals obtained for water-air flow using gamma ray absorption. The presented method was illustrated by use data collected in experiments carried out on the laboratory hydraulic installation with a horizontal pipe, equipped with two Am-241 radioactive sources and scintillation probes with NaI(Tl) crystals. Signals obtained from detectors for slug, plug, bubble, and transitional plug – bubble flows were considered in this work. The recorded raw signals were analyzed and wavelet energy was extracted using multiresolution analysis. It was found that energies of wavelet approximation at 1-5 levels are useful to recognize the structure of the flow.
Investigation of the mechanisms of sea spray generation induced by wind-wave interaction in laboratory conditions
Authors: Kandaurov Alexander , Sergeev Daniil , Troitskaya Yuliya , Ermakova Olga
Published: June 2019

The paper presents the results of investigations of the mechanisms of spray of droplets generation within wind wave interaction obtained under laboratory conditions on the High-speed Wind-Wave Flume of the Institute of Applied Physics of the Russian Academy of Sciences. For the research, a multi-angle high-speed video system used together shadow method, including underwater illumination. The results allowed for the classification of mechanismsleading to the formation of droplets. Three main types of phenomena responsible for the generation of the spume droplets near the wave crest were specified: breakage of liquid ligaments, bursting of large submerged bubbles, and bag breakup. The last and less known mechanism claims to be dominant for high wind speeds and it was described in detail.
Influence of partial immersion on steel plate dynamic properties
Authors: Kůrečka Jan , Habán Vladimír
Published: June 2019

Eigenfrequency of object drops when it is submerged in the water compared to an air exposition. In this article the eﬀect of partial submersion on dynamic properties of steel plate is investigated. Changes diﬀer by a type of particular modeshape because of relative position of nodes and antinodes to free surface. Dynamic properties are influenced mainly by position of antinodes, in which maximal displacement occurs. Comparison of experiment, FEM simulation in ANSYS and custom code analytical solution is presented. Added eﬀects of fluid on the steel plate are discussed.
The simulation tests of the flow in the device stabilizing the working pressure of the cement slurry
Authors: Nowakowski Lukasz , Depczyński Wojciech , Blasiak Slawomir
Published: June 2019

The article describes research carried out for design and construction of devices stabilizing the working pressure of cement slurry, with use of Deep Soil Mixing technology. The paper presents also the results of numerical calculations showing the flow in the device stabilizing the working pressure of the cement slurry. Flow simulation tests were carried out in the ANSYS program.
Pool boiling heat transfer for surfaces with microchannels of variable depth
Authors: Pastuszko Robert , Bedla-Pawlusek Milena , Kaniowski Robert
Published: June 2019

Experimental investigations of pool boiling heat transfer on microchannels of variable depth were conducted. The experiments were carried out for water and ethanol at atmospheric pressure. Microchannels of variable depth from 0.2 to 2.8 mm and width 0.5 mm were uniformly spaced on base surface with pitch of 1 mm. The comparison of heat transfer coefficients for surfaces with variable and constant depth of microchannels was made. At the low and medium heat fluxes structures with constant microchannel depth showed the best boiling heat transfer performance. EX-FH20 (Casio) camera was used to record the images of the entire surface of the specimen. The bubble growth mechanism on the enhanced surface was different from that of plain surface. Visualization investigations were aimed at identifying nucleation sites and determining the bubble growth cycle. Vapor bubbles generate in microchannel spaces, from where they move towards the fin tips, then grow and depart.
Using POD method in experiments with convection flow on the cube benchmark
Authors: Sergeev Daniil , Kandaurov Alexander
Published: June 2019

Investigations of the flow structure on the benchmark “cube” under conditions of natural convection caused by a vertical temperature gradient are performed using a low cost PIV-measuring system with continuous laser. The obtained velocity fields were processed with POD method to obtain typical structures (modes) in the flow. It is shown that the steady flow can be described by combination of the first three modes. It is demonstrated that only starting with the third mode there is a significant change in the spectra of the amplitude coefficients of the modes, the peak shifts to the region of higher frequencies. Thus accounting for this mode is essential for describing turbulent processes in the system and verification of numerical calculations. Comparison with the results of the LES simulation performed using the Ansys CFX package (taking into account the results of processing the experimental data by the POD method) demonstrated good agreement both in the structure of the modes and in their frequency spectra.
Thermo-capillary flow in a Hele-Show cell as a tool for research of the dynamics of insoluble surfactant monolayer
Authors: Shmyrov Andrey
Published: June 2019

The occurrence of thermocapillary convection in a Hele-Shaw cell in the presence of the surfactant film on the free surface is experimentally investigated. It is shown that at certain values of the control parameter two different zones are formed on the surface – the zone free from impurities and the stagnant zone. In the first zone, the onset and development of an intense Marangoni convection is observed, while in the stagnant zone the velocity of the motion on the surface is lower by about two orders of magnitude. This study clearly demonstrates that the analysis of the temperature profile provides sufficient information about both the distribution of tangential stresses over the surface and the degree of compression of the surfactant film. In addition, due to a simple linear law of temperature variation on the surface of the stagnant zone, the distribution of the surfactant molecules over the surface can be predicted based on the known equation of state for the film of the examined surfactant. Thus, the application of a set of simple experimental techniques to the examined model problem allowed us to obtain complete information on the state of a complex system consisting of a liquid layer and a surface film of the surfactant, the structure of the volumetric flow, the velocity of the liquid at the surface, the distribution of shear stresses and surfactant molecules over the surface.
Investigation of the velocity field downstream of a benchmark vent using numerical simulation and hot-wire anemometry
Authors: Sip Jan , Lizal Frantisek , Elcner Jakub , Pokorny Jan , Jicha Miroslav
Published: June 2019

The velocity field in the area behind the automotive vent was measured by hot-wire anenemometry in detail and intensity of turbulence was calculated. Numerical simulation of the same flow field was performed using Computational fluid dynamics in commecial software STAR-CCM+. Several turbulence models were tested and compared with Large Eddy Simulation. The influence of turbulence model on the results of air flow from the vent was investigated. The comparison of simulations and experimental results showed that most precise prediction of flow field was provided by Spalart-Allmaras model. Large eddy simulation did not provide results in quality that would compensate for the increased computing cost.
Possibility of use adsorption chillers for increase efficiency in conventional power plant
Authors: Sztekler Karol , Kalawa Wojciech , Nowak Wojciech , Stefański Sebastian , Krzywański Jarosław , Grabowska Karolina , Mika Łukasz
Published: June 2019

Long-term forecasts indicate that the annual increases in electricity demand by 2030 will be approx. 2 ÷ 3% a year. At present, 40% of the world's electricity is produced using coal-fired power plants. Forecasts indicate that coal will still be the predominant fuel used to produce electricity and thus any actions aimed at increasing the efficiency of electricity production are purposeful. Enormous amounts of waste heat, which is not sufficiently used, are released during the process of electricity production. One of the ways to manage it is to use refrigeration systems based on adsorption chillers which would use waste heat to generate cold that would be employed for air-conditioning or process purposes. In this paper, the cycle of a conventional coal-fired power plant was modelled and then the possibilities of using waste heat for generation of cold as well as the impact of a chiller on the operation of a power unit were analysed using IPSEpro software.
Application of various 'response surface' based algorithms in optimization of air manifolds for batch boilers
Authors: Szubel Mateusz , Filipowicz Mariusz , Mikrut Anna
Published: June 2019

Correct design of air manifolds applied in biomass-fired batch boilers allows to avoid excessive emissions and high flow resistance, as well as helps achieving the required parameters of the fan supplying air to the boiler. The paper describes the process and the results of the optimization performed using selected methods based on the response surface analysis. An experimentally validated CFD model of the state of the art air manifold has been geometrically parametrized, in order to find the shape that is optimal from the point of view of the objective function. In each analysis, the objective function was linked to air flow characteristics. Selected algorithms of the interpolation of design points that were obtained as the result of the numerical experiment have been compared and evaluated. Optimization using the response surface generated using various algorithms has been performed and verified by further direct CFD computations. The obtained optimal values of the input parameters were applied in the final model of the prototype. The flow characteristics of the prototype and the reference state have been compared and discussed. Significant improvement of the operation conditions has been achieved.
Analysis of the possibility of using high-speed pneumatic directional valves to regulate the flow of compressed air
Authors: Takosoglu Jakub
Published: June 2019

Most often, proportional flow valves or flow servovalves are used for position control of pneumatic drives. In case of this type of valves, flow characteristic of the valve represents a dependence of flow rate upon analogue control signal (voltage or current). The paper presents experimental studies of two high-speed pneumatic 3/2 directional valves (3-way 2-position) in order to determine the flow characteristics and flow parameters. One has analysed the option to use the directional valves to control the flow rate of compressed air using frequency-based signals.
Melting n-eicosane in scaled-up model of capsule for use in hot climate thermal-comfort garments
Authors: Tesař Václav , Kordík Jozef
Published: June 2019

Recent ideas in development of garments for thermal comfort in desert climates concentrate on textile containing small capsules filled with material melting to store latent heat at roughly human body temperature. This cools the garment wearer during the hot day and later keeps him warm in the cold desert night. This article investigates the melting process in a single scaled up model of spherical capsule filled with n-eicosane – a material melting at Tm = 35.7 ˚C. In the experiment, the capsule model was heated starting from the initial temperature 30˚C by warm water at 50.4 ˚C. The large scale of the model made possible study of details of the melting process.
Effect of pipe inclination on flow behaviour of fine-grained settling slurry
Authors: Vlasak Pavel , Chara Zdenek , Matousek Vaclav , Konfrst Jiri , Kesely Mikolas
Published: June 2019

The effect of flow parameters of fine-grained settling slurry on the pressure drop-velocity relationship, deposition limit velocity and local concentration distribution was studied in an experimental pipe loop of inner diameter D = 100 mm with inclinable pipe sections for pipe inclination ranging from – 45° to +45°. The slurry consisted from water and narrow particle size distribution glass beads of mean diameter d50 = 0.18 mm. The concentration distribution was studied with application of a gamma-ray densitometry. The deposition velocity was defined as the flow velocity at which stationary deposit started to be formed at the pipe invert. The study revealed the stratified flow pattern of the studied slurry in inclined pipe sections, for slurry velocities below to the deposition limit sliding or stationary bed were created in ascending pipe sections. For low pipe inclination (α < ± 25°) the effect of inclination on local concentration distribution was not significant. Mean transport concentration for descending flow was lower than that for the ascending flow Deposition limit in inclined pipe was slightly lower than that in horizontal pipe. Frictional pressure drops in ascending pipe were higher than that in descending pipe, the difference decreased with increasing velocity and inclination.
Studies of properties of the seat suspension system with air spring
Authors: Woś Piotr , Dindorf Ryszard
Published: June 2019

This article presents issues related to the study of the seat vibration isolating properties of the working machine. The spring force of the suspension system is realized by means of a pneumatic spring. The mathematical model of the air spring is presented. The results of research presented in the form of power spectral density of the vibration acceleration of the suspension system.
The study of water-head measurement shown in a single tube manometer by use of easy image-processing technique
Authors: Yokoi Yoshifumi
Published: June 2019

This study proposes the technique which can perform pressure measurement by the low flow velocity which is performed by flow visualization. The technique is the following. The water level image accompanied by the scale shown in a single tube manometer is photographed with a digital camera or a digital camcorder. And image-processing measurement of the image data is carried out in the length of the water level by computer. As verification of the technique, the measurement comparison result of the pressure distribution on the surface of a circular cylinder set in the stream was compared with the previous result. The result was good. It proved that the technique is measurable also by a minute water-head. Furthermore, examination was performed about the validity, the reliability, and the operativity of the technique. As a result, even if who did operation of image-processing measurement, it was shown that high resolution and good accuracy are obtained.
A posteriori error estimates for Darcy’s problem coupled with the heat equation
Authors: Dib Séréna , Girault Vivette , Hecht Frédéric , Sayah Toni
Published: June 2019

This work derives a posteriori error estimates, in two and three dimensions, for the heat equation coupled with Darcy’s law by a nonlinear viscosity depending on the temperature. We introduce two variational formulations and discretize them by finite element methods. We prove optimal a posteriori errors with two types of computable error indicators. The first one is linked to the linearization and the second one to the discretization. Then we prove upper and lower error bounds under regularity assumptions on the solutions. Finally, numerical computations are performed to show the effectiveness of the error indicators.
Damage mechanisms assessment of hybrid carbon/flax fibre composites using acoustic emission
Authors: Ben Ameur Mariem , Rebiere Jean-Luc , El Mahi Abderrahim , Beyaoui Moez , Abdennadher Moez , Haddar Mohamed
Published: June 2019

The purpose of the present experimental study is to describe the damage mechanisms occurring in epoxy matrix composites reinforced with hybrid carbon-flax fibres. The samples tested were consist of unidirectional carbon and flax fibre plies with different stacking sequences. Composite laminates were manufactured by hand lay-up process. The specimens were tested under uniaxial tensile loading. The tests carried out were monitored by the acoustic emission (AE) technique. The results obtained during the monotonic tensile tests were analyzed in order to identify the damage mechanisms evolutions. The recorded events were classified with the k-means algorithm which is a statistical multivariable analysis. In addition, it was an unsupervised classification according to temporal descriptors. The percentage of each damage mechanism to the global failure was evaluated by the hits number and the acoustic energy activity. The AE technique was correlated with scanning electron microscopy (SEM) observations to identify the typical damage mechanisms.
Travel-time correction and preliminary results for ocean acoustic tomography in South China Sea
Authors: Ji Xingyu , Zhao Hangfang
Published: June 2019

An acoustic tomography trial experiment was conducted in South China Sea during May to August in 2016. Two moorings are installed apart from about 56.94 km, while each consists of one low frequency source, 20 hydrophones deployed from the depth of about 400 m to 1600 m, total 32 depth sensors and 3 compass and tilt sensors. Due to internal waves and currents in this area, as a typical value, horizontal drift of a mooring can reach 300 m, thus moorings drift need to be considered to correct ray travel-time. In this paper, the shape of a mooring is estimated firstly and locations of all hydrophone array elements are then calculated and finally used to determine travel-time perturbation of acoustic arrivals. The mooring is modelled as 2 curves, while the end of the mooring is fixed at the cement anchor on the sea floor. Optimization is used to acquire hydrophone location inferential solution. The inferred shape of hydrophone array and element locations are used to correct the travel-times measured in the experiment. We find that corrected travel-times match the trend of the change of sound speed profile better in the sea. Finally, the corrected travel-times are used to tomography of sound speed profile. AR (Autoregressive) process is used to describe the dynamic evolution of sound speed profile and Kalman filter is applied in the sequential estimation. The performances of the time-independent method and the method using AR process and Kalman filter are compared, reasonably the latter is better than the former in particular with abundant measured data.
Assessment of multi-target distinguishing using deconvolved conventional beamforming
Authors: Lan Hualin , Zhang Xueqi , Li Ruonan , Jin Suyu , Li Na
Published: June 2019

Multi-target distinguishing based on beamforming is a popular topic in array signal processing. Conventional beamforming as a frequently used method is robust but constrained by the Rayleigh limit. Deconvolved conventional beamforming is a better choice since point scattering function could be derived by deconvolution based on Lucy-Richardson, with narrower beam width and lower sidelobe levels. Besides, the robustness of the conventional beamforming is maintained. In this paper, a new method of combined deconvolved conventional beamforming with Dolph-Chebyshev weights is proposed. The proposed method could overcome the deficit of deconvolved conventional beamforming on low mainlobe of weak target caused by iteration. Firstly, principles of the method are given including conventional beamforming, deconvolved conventional beamforming and the proposed algorithm combined deconvolved conventional beamforming with Dolph-Chebyshev weights. Then, performance of the proposed method for bi-target signals with the equivalent strength, in terms of the effect of signal frequency on distinguishing performance of two closed spaced targets coexisted is analysed. For weak target detection existed strong interference, the superiority of the proposed algorithm is analysed. Finally, proposed method is validated with sea trial data of two ship target noise recorded by a 48-element array.
Performance assessment of a small-size ocean wave energy harvester
Authors: Sang Yongjie , Dubus Bertrand
Published: June 2019

A lightweight electromechanical device is studied to harvest energy of ocean waves and supply electrical power to small-size ocean observation equipment such as sonobuoys. It is composed of a magnet fixed to the floating housing which follows the motion of the ocean surface and a moving coil connected to the case via a flexible spring. As the floating housing follows the vertical motion of water surface, a voltage is induced in the coil due to relative velocity between the coil and the magnet, and kinetic energy of the ocean wave is converted into electrical energy. Full bridge rectifying circuit and smoothing capacitor are used to convert AC voltage to constant voltage. Single degree of freedom electromechanical model of the prototype transducer (LGT-4.5 geophone) is developed and simulated with an electrical circuit software to predict energy harvesting performance. Vibration experiments are also performed with a shaker to validate transducer model and quantify output voltage. Parametric analysis is conducted to identify optimal choice of capacitance in terms of maximum stored energy and minimum charging time. This device is simple and small size relative to ocean wavelength compared to classical linear permanent magnetic generator used in offshore power plant. Its power generation per unit weight is compared to larger scale ocean energy converters.
Numerical calculation and measurement for the focus field of concave spherical acoustic lens transducer
Authors: Zhang Jun , Chen Yi , Yang Liuqing
Published: June 2019

How to accurately calculate the sound field formed by acoustic lenses is an important basis for the design of acoustic lens transducers. The radiation sound field distribution of the physical model of acoustics lens is simulated by numerical methods, including the ray propagation method and the wave propagation method. The ray propagation method can only get the focal length without considering the wave characteristics property, while the wave propagation method takes into account the amplitude and phase factors of the wave, and by which the distribution of the whole sound field can be got. The relationship between the property of refractive wave and incident angle of incident wave is analyzed, and theoretical results of the distribution of the focal field are obtained. The actual sound field of the real transducer is measured by acoustic field scanning system, and the measured results of focal length and focal area are obtained. The comparison and analysis of the numerical data and measured data show that the wave propagation method can be used to predict the focus field of concave spherical acoustic lens transducer accurately and effectively.
Horizontal spatial correlation of reverberation for rough sea-bottom interface
Authors: Yan Shanyong , Wang Changhong
Published: June 2019

Correlation sonar, which estimates the velocity of vessel utilizing the principle of waveform invariance, can achieve the sampling of the horizontal spatial correlation of sea-bottom reverberation. The horizontal spatial correlation can be expressed as a correlation function and is affected by sea-bottom characteristics. The expression of the correlation function of the sea-bottom reverberation is derived, which is written as the convolution of the autocorrelation function of transmitted signal, the cross-correlation function of the backscattered impulse response from a plane interface, and the autocorrelation function of the probability density function of the sea-bottom roughness. The isotropic interface roughness of the sea-bottom leads to a circular planform of the correlation function whose width varies with roughness. The anisotropic interface roughness of the sea-bottom leads to an elliptical planform of the correlation function whose major axis is in the direction of weaker roughness. Simulation of submarine reverberation and correlation function verifies this conclusion. The model for the spatially covariant field is used to estimate the backscattering cross section which varies with azimuth angle under the condition of anisotropic seafloor roughness. It should be noted that the horizontal spatial correlation of reverberation is also related to sonar parameters and other sea-bottom characteristics.
Numerical study of a control scheme on flow-induced cavity noise
Authors: Liu Lulu , Liu Jin , Lyu Shijin
Published: June 2019

A numerical procedure for flow induced cavity noise is established in the paper. The procedure is based on large eddy simulation and FW-H acoustic analogy. The computational scheme is validated by comparing with experimental data. The change of flow induced noise along with cavity length, cavity depth and velocity is studied. A noise control scheme, which includes upright grille and oblique grille, is designed for reducing the flow-induced cavity noise. It turns out that the oblique grille shows superiority in the reduction of cavity noise by modifying the flow structure of the sheat layer.