bluuebunny/crossref_metadata_2025 huggingface dataset:
Achieving high performance and stable inverted planar perovskite solar cells using lithium and cobalt co-doped nickel oxide as hole transport layers
Authors: Wang Shaoxi , Zhang Bingjuan , Feng Dan , Lin Zhenhua , Zhang Jincheng , Hao Yue , Fan Xiaoya , Chang Jingjing
Published: June 2019

Herein, we demonstrate that lithium and cobalt co-doped NiOx hole transport layers can greatly enhance the device performance of inverted planar heterojunction perovskite solar cells.
Evidence for the dynamic relaxation behavior of oxygen vacancies in Aurivillius Bi2MoO6 from dielectric spectroscopy during resistance switching
Authors: Guo Fei , Zhao Mengting , Xu Kang , Huan Yu , Ge Shuaipeng , Chen Yiming , Huang Jiahao , Cui Yimin , Zhuang Jincheng , Du Yi , Feng Haifeng , Hao Weichang
Published: June 2019

The resistive switching behavior of oxygen ion conductor Bi2MoO6 were investigated by dielectric spectroscopy.
Age-Related Changes in Speech Recognition Performance in Spanish–English Bilinguals' First and Second Languages
Authors: Desjardins Jamie L. , Barraza Elisa G. , Orozco Jordan A.
Published: June 2019

Purpose

The purposes of the current study were to examine the effect of age on Spanish–English bilinguals' speech recognition performance and to identify differences in speech recognition performance between Spanish and English bilinguals' 1st and 2nd languages.

Method

Fifteen younger adult Spanish–English bilinguals, 15 older adult Spanish–English bilinguals, 15 younger adult English monolinguals, and 15 older adult English monolinguals participated in this study. Bilingual participants had learned Spanish from birth and began learning English by the age of 4 years (
SD
= 2.7). Speech recognition performance was measured using the Spanish and English versions of the Hearing in Noise Test (HINT;
Nilsson, Soli, & Sullivan, 1994
) presented in quiet and in a speech-shaped background noise. Participants also completed a self-assessment of the listening effort they expended on the HINT in background noise.

Results

There were no significant differences in performance within or between the participant groups for the HINT in quiet. In background noise, Spanish–English bilinguals performed significantly poorer and had increased listening effort on the English HINT than English monolinguals, with the most significant effects evidenced for the older Spanish–English bilingual group. Overall, the bilingual participants performed significantly better and expended less listening effort on the Spanish than on the English HINT in background noise, despite learning both languages at an early age.

Conclusions

Older Spanish–English bilinguals are at an increased disadvantage in understanding English in background noise compared to older English monolinguals. This suggests that current clinical audiological evaluation and treatment procedures may need to be modified to better serve an older bilingual population.
Pitch Shifting With the Commercially Available Eventide Eclipse: Intended and Unintended Changes to the Speech Signal
Authors: Heller Murray Elizabeth S. , Lupiani Ashling A. , Kolin Katharine R. , Segina Roxanne K. , Stepp Cara E.
Published: June 2019

Purpose

This study details the intended and unintended consequences of pitch shifting with the commercially available Eventide Eclipse.

Method

Ten vocally healthy participants (M= 22.0 years; 6 cisgender females, 4 cisgender males) produced a sustained /ɑ/, creating an input signal. This input signal was processed in near real time by the Eventide Eclipse to create an output signal that was either not shifted (0 cents), shifted +100 cents, or shifted −100 cents. Shifts occurred either throughout the entire vocalization or for a 200-ms period after vocal onset.

Results

Input signals were compared to output signals to examine potential changes. Average pitch-shift magnitudes were within 1 cent of the intended pitch shift. Measured pitch-shift length for intended 200-ms shifts was between 5.9% and 21.7% less than expected, based on the portion of shift selected for measurement. The delay between input and output signals was an average of 11.1 ms. Trials shifted +100 cents had a longer delay than trials shifted −100 or 0 cents. The first 2 formants (F1, F2) shifted in the direction of the pitch shift, with F1 shifting 6.5% and F2 shifting 6.0%.

Conclusions

The Eventide Eclipse is an accurate pitch-shifting hardware that can be used to explore voice and vocal motor control. The pitch-shifting algorithm shifts all frequencies, resulting in a subsequent change in F1 and F2 during pitch-shifted trials. Researchers using this device should be mindful of stimuli selection to avoid confusion during data interpretation.
Drone detection and radar‐cross‐section measurements by RAD‐DAR
Authors: de Quevedo Álvaro Duque , Urzaiz Fernando Ibañez , Menoyo Javier Gismero , López Alberto Asensio
Published: June 2019

RAD‐DAR is a frequency‐modulated‐continuous‐wave radar demonstrator, working at X‐band, completely designed and constructed by the authors’ research group following the ubiquitous‐radar concept. After introducing its main hardware and software blocks, with special emphasis to its off‐line signal processing and data processing, this study presents the results of a drone detection test, where RAD‐DAR achieved a DJI‐Phantom 4 detection and tracking at a range up to 3 km. The system performance is discussed with different flights including an attack manoeuvre, and a free flight, which helps to highlight their advantages in surveillance tasks due to the RAD‐DAR staring nature. Furthermore, range, speed and azimuth accuracies are discussed, considering the drone global positioning system data. Finally, this study shows a statistical radar cross‐section study based on the processed data of the drone and attempts to classify this target by means of Swerling models.
Reinforcement learning method for plug‐in electric vehicle bidding
Authors: Najafi Soroush , Shafie‐khah Miadreza , Siano Pierluigi , Wei Wei , Catalão João P.S.
Published: June 2019

This study proposes a novel multi‐agent method for electric vehicle (EV) owners who will take part in the electricity market. Each EV is considered as an agent, and all the EVs have vehicle‐to‐grid capability. These agents aim to minimise the charging cost and to increase the privacy of EV owners due to omitting the aggregator role in the system. Each agent has two independent decision cores for buying and selling energy. These cores are developed based on a reinforcement learning (RL) algorithm, i.e. Q‐learning algorithm, due to its high efficiency and appropriate performance in multi‐agent methods. Based on the proposed method, agents can buy and sell energy with the cost minimisation goal, while they should always have enough energy for the trip, considering the uncertain behaviours of EV owners. Numeric simulations on an illustrative example with one agent and a testing system with 500 agents demonstrate the effectiveness of the proposed method.
Smart household management systems with renewable generation to increase the operation profit of a microgrid
Authors: Hakimi Seyed Mehdi , Saadatmandi Mohammad , Shafie‐khah Miadreza , Catalão João P.S.
Published: June 2019

During the past few years, due to the growth of electric power consumption, generation costs as well as rises in the level of greenhouse gases efficiency bring special focus on distributed generation. Developing distributed generation resources, especially renewable energy resources, is one of the safest ways to solve such problem. These resources have been decentralised by being installed close to the houses producing few kilowatts. Therefore, there are no losses in transmission lines and provide response for demand. Based on their benefits, the use of such energy resources should be developed in the future, but its management and optimal use is a major challenge. This has become one of the main concerns ofenergy systems researchers. In the current study, an innovative model is provided as a strategic management. It is intended to optimise the operation in smart homes consisting of generation units such as a wind turbine, solar panels, storages, and un/controllable loads. The main objective of this optimisation management is to maximise microgrid profitability for 24 h. The overall results of the model proved that the profit of microgrid increased significantly.
Online data‐driven approach of yaw error estimation and correction of horizontal axis wind turbine
Authors: Xue Jianguo , Wang Lu
Published: June 2019

Active yaw system is a very important component of modern horizontal axis wind turbines to keep the nacelle aligning with the stochastic wind direction. However, in practice, it is hard to keep the rotor facing into the wind precisely, which will lead to not only the loss in power production but the increment in aerodynamic loads. This study presents a data‐driven approach to estimate yaw error for remote terminal unit.
Multiple DRPs to maximise the techno‐economic benefits of the distribution network
Authors: Sharma Sachin , Niazi Khaleequr Rehman , Verma Kusum , Meena Nand Kishor
Published: June 2019

This study addresses a demand response programme (DRP) model considering the price elasticity of demand to determine the peak scheduling for different categories of consumers with the possibility of load shifting. The main objective is to minimise daily energy loss and improvement in the node voltage profile of distribution system along with the economic benefits of different stakeholders. The proposed work helps in appropriate selection of DRP for different feeders/consumers. The investigations are performed on a benchmark 33‐bus test distribution system and comprehensive analysis is illustrated through simulation results.
Investigation of SSO characteristics in grid‐connected PMSGs system
Authors: Huang Biyue , Wang Long , Sun Haishun , Liu Yuming , Chen Yahao
Published: June 2019

In recent years, a new type SSO issue, which has occurred in direct‐drive permanent magnetic synchronous generators (PMSGs) based wind farm, brings a new challenge to the stability of the power system. In this paper, the SSO issue in grid‐connected PMSGs system is studied by the eigenvalue analysis. The linearised state‐space model of this system is built firstly. The impacts on the SSO characteristics from short‐circuit ratio (SCR), impedance‐frequency characteristic, resonant frequency of AC network and control parameters of PMSGs are observed by the root loci analysis. After that, electromagnetic transient simulation is carried out to verify the eigenvalue analysis. Meanwhile, the participation factors of SSO mode are calculated to analyse the subsynchronous control interaction (SSCI) between AC network and PMSG. The result shows that there is a SSO mode which is greatly influenced by AC network and DC capacitor, grid side converter (GSC) control of PMSG. The characteristics of AC network will affect the SSCI between AC network and PMSG.
Impact analysis of different charging models for optimal integration of plug‐in electric vehicles in distribution system
Authors: Singh Jyotsna , Tiwari Rajive
Published: June 2019

Due to rising environmental concerns and desire to achieve energy independence, the government of many countries across the world keen on promoting plug‐in electric vehicles (PEVs). Consequently, high penetration of PEVs is expected in the imminent future. This work aims to develop models with the vehicle‐to‐grid operation of PEVs under different scheduling strategies namely, load stabilising model, charging/discharging cost model, battery degradation model and mixed‐objective model, respectively. Further maximum penetration of PEVs corresponding to each scheduling model is evaluated. The impact of PEVs scheduling models on distribution system operational parameters such as peak load, transformer loading, distribution line limits and losses is also investigated. And finally, a comparative analysis of charging models in terms of technical and economic benefits is presented. The proposed model is implemented on the 38‐node distribution system and simulation results demonstrate the comprehensive evaluation of proposed charging models.
Building a bridge between industry and theory on the example of a new ventilation system
Authors: Peszyński Kazimierz
Published: June 2019

The paper presents the possibilities of simplified determination of the air volumetric flow rate in ventilation ducts. This problem occurred during the tests of local losses in the elements of a new ventilation system based on ducts with a rounded rectangular cross-section. The presented method requires mathematical modelling of the flow velocity distribution in the ducts. The paper presents four models of the velocity distribution. The necessity of using so many models resulted from the wide coverage of the tested sections: Amax/Amin= 46.88.
CFD MODELLING OF INDUSTRIAL AIR CURTAINS WITH HEATING UNIT
Authors: Aksoy Muharrem Hilmi , Yagmur Sercan , Dogan Sercan
Published: June 2019

Industrial air curtains are used to prevent air from moving from one space to another space or to environment. The most common used type is downward-facing blower fan mounted over the entrance of a building, or an opening door between two spaces conditioned at different temperatures. In many factories and industrial buildings, heating or cooling applications are difficult due to the huge doors. These huge doors cause heat loses with convection phenomena of the inside air. In this study an air curtain having heater unit is analyzed numerically by CFD. The height of the air curtain from the bottom side is vary between 2.5 m, 3 m, 4m, 5m and 6 m mounted over the entrance door of the conditioned volume. For CFD studies proper mesh structure is created on the flow domain and Shear Stress Transport (SST) k-omega models were used in Unsteady Reynolds Averaged Navier-Stokes (URANS) computations. The blowing temperature of the air curtain has adjusted to 60 °C with the inside temperature was aimed to kept at +7°C while the outside temperature was -5°C. It is found that there is less flow occurred to the environment from conditioned volume at 2.5 3, 4 and 5 meter height cases. In these cases, the air curtain also contributes the heating of the conditioned room. But some ratio of the air flows through the atmosphere and the room cannot kept at the +7°C initial temperature at 6 m case. It is also found that the heating ratio at different blowing heights differs between 0,89-1,98 comparing the case without an air curtain.
Dispersion kinetics in mechanically agitated vessel
Authors: Bucciarelli Elia , Formánek Roman , Kysela Bohuš , Fořt Ivan , Šulc Radek
Published: June 2019

Agitation of two immiscible liquids or solid-liquid suspension is a frequent operation in chemical and metallurgical industries. Prediction of mean drop/particle size and drop/particle size distribution (DSD) is vital for emulsification, suspension polymerization, solid particle dispersion or crystallization. Simulation of particulate systems requires the knowledge of DSD and its time evolution. The time evolution of drop size distribution was investigated in baffled vessel mechanically agitated by a Rushton turbine and a high-shear tooth impeller. The system water –silicone oil was used as a model liquid. The volume fraction of the dispersed phase was 0.047 %. The drop sizes were determined by image analysis. The time evolution of the drops size dp32 was studied for both impellers tested. The model used involves the first order kinetics. Finally, the following correlations predicted by the Kolmogorov-Hinze theory were evaluated at steady state: dp32/D = C1.We-0.6 and dpmax/D = C2.We-0.6, where We is the impeller Weber number.
Steady and transient flow structure in a rotameter with a ball float
Authors: CANLI Eyub , ATES Ali
Published: June 2019

Dimensions and material specifications of a commercial rotameter were used for investigating steady and transient flow structure in a rotameter with a ball float. Since drag coefficient of sphere versus Reynolds number is well known and the range of the commercial rotameter is given, the investigation relies on strong validation data. An axially symmetric geometric model is used for steady analysis of the system as the initial step of the investigation. Assessing the proper mesh structure and turbulence model is aimed for this step. Then full three dimensional solid model is put into transient analysis with RANS and LES models. Vortex shedding frequency, Strouhal number and drag coefficient values are evaluated. Vortex induced vibrations are assessed according to transient results. The work is a preliminary study for future investigation on rotameter floats. The framework of future studies is also presented.
Experimental Verification of Pneumatic Cylinder External Pneumatic Cushioning
Authors: Dvořák Lukáš , Fuksa Lukáš , Ledvoň Marian , Brzezina Petr
Published: June 2019

This paper deals with the possibilities of the pneumatic cylinder piston end-position cushioning. The introductory part describes the cushioning methods - elastic, hydraulic and internal pneumatic. The second part describes the external pneumatic cushioning, its experimental verification and the measurement results for a specific case.
On The Effect Of The Shape Of Buildings And Chimneystacks On Ventilation And Pollutant Dispersion
Authors: Ferrari Simone , Badas Maria Grazia , Garau Michela , Salvadori Luca , Seoni Alessandro , Querzoli Giorgio
Published: June 2019

The purpose of this work is to investigate the modifications induced by the change of the roof shape in the flow field, inside and above the buildings, with an attention to their capability to modify the air quality and the dispersion of pollutants released from chimneystacks. We have carried out laboratory experiments on arrays of identical buildings, with symmetrical dual-pitched or flat roofs, and chimneystacks of different heights and positions. The experiments have been carried out in a close-loop water-channel, where two non-intrusive and quasi-continuous in space Digital Image Analysis technique have been implied to measure the velocity fields (Feature Tracking Velocimetry) and the concentration fields (Laser Induced Visualization). Results have highlight the meaningful role of gabled roofs in modifying turbulence, which increases the air exchange rate between the street canyon and the outer flow, but, in some conditions, they increase the dragging of pollutant inside the canyon. These results can have an immediate practical impact on the building design and on planning strategies, as the roof shape can be a useful tool to enhance natural ventilation and pollutant, humidity and/or heat dispersion, i.e. the air quality in urban and industrial areas.
Image analysis of particle size: effect of light source type
Authors: Formánek Roman , Kysela Bohuš , Šulc Radek
Published: June 2019

Agitation of two immiscible liquids or solid-liquid suspension is a frequent operation in chemical and metallurgical industries. The sizes of particles, bubbles or droplets can be determined by the Image Analysis Technique. It is known that the quality of captured images depends significantly on the original image background that is mainly affected by the type of the light source. The aim of this contribution is to investigate the effect of light source type on image quality. The four types of light sources were tested: 1) 1000 W halogen lamp, 2) 72 W LED bar panel, 3) 60 W LED chip, and 4) 90 W LED chip. The illumination intensity and image background quality were investigated for each tested light sources. The effect of the shutter speed on evaluated particle sizes was tested using monodisperse spherical calibration particles having diameter of 1.19 mm. The difference observed between particle sizes evaluated by image analysis for given light source and declared calibration particle diameter was used as a measure of light source quality.
The effect of material mixing on heat transfer in the process of contact drying
Authors: Havlík Jan , Dlouhý Tomáš
Published: June 2019

This paper deals with the process of heat transfer in contact drying. Heat transfer during contact drying for a stagnant bed without mixing and drying with a mechanically agitated bed were theoretically and experimentally investigated for a contact paddle dryer. The effect of material mixing on the process of heat transfer was evaluated. For a theoretical description of heat transfer in a contact dryer, the penetration model was used. Experiments with green wood chips were realized on an experimental paddle dryer. In both cases, the stagnant bed and the mechanically agitated bed, the theoretical values were slightly higher compared to the experimental results. Mixing intensifies the process, it showed an increase to roughly twice in heat transfer for the tested experimental dryer.
Determining the thickness of sludge on the heat exchanger tube inside an anaerobic digester
Authors: Hożejowski Leszek , Teleszewski Tomasz Janusz
Published: June 2019

The paper presents a simplified method of determining the thickness of sludge on the walls of the heat exchanger piping in a biogas plant digester. The evaluation of the thickness of a sludge layer is based on the biogas plant operation parameters, including the inlet and outlet temperature of the heat exchanger, mass flow and the geometric characteristics of the heat exchanger and physical parameters of the substrate working inside a fermentation chamber. Measurement of the thickness of the sludge layer on the walls of a heat exchanger is only possible at the time of general cleaning of a digester, which necessitates switching off the biogas plant operation. The paper compares the results of predictions with experimental data of the work of a biogas plant digester located in north-eastern Poland, in Ryboły. The presentation of the obtained numerical results is supplemented by the uncertainty analysis. The significance of undertaking such research lies in its applicational aspects, as during the operation of a biogas plant sludge accumulates on the walls of a digester, which provides additional thermal resistance and reduces the thermal efficiency of the heat exchanger.
Measurement of drop size distribution time rate for liquid-liquid dispersion using IPI method
Authors: Jasikova Darina , Kotek Michal , Kysela Bohus , Sulc Radek , Kopecky Vaclav
Published: June 2019

The liquid-liquid dispersion properties are studied mainly by image analysis (IA) and Interferometric Particle Imaging (IPI). Drop sizes will be investigated in dilute dispersion since in this case the break up phenomena is the dominating and is not affected by phase fraction. Characteristics of the size distribution and the evolution of two liquid-liquid phase’s disintegration were studied. The IPI method was used for subsequent detailed study of the disintegrated droplets. We compared two liquids: Rhodosil Oil 47V50, and Silicone Oil AP1000 under stirrer rate of 540 rpm, and 760 rpm. The experiment run in the scaled model of agitated tank with Rushton turbine.
Spectral characteristics of turbulent boundary layers – comparison of Particle Image Velocimetry and Thermal Anemometry
Authors: Jurčáková Klára , Kellnerová Radka , Procházka Pavel , Antoš Pavel
Published: June 2019

Flow in turbulent boundary layers over various rough surfaces was measured by the time-resolved particle image velocimetry and the thermal anemometry. The experimental methods showed very good agreement in both mean and spectral characteristics taking into account each method limitations. The spectral characteristics supported the attached eddy hypothesis. The most energetic structures were growing with the wall-normal distance and they achieved sizes equal to 3 to 8 boundary layer depths.
Study of pool boiling heat transfer with FC-72 on open microchannel surfaces
Authors: Kaniowski Robert , Pastuszko Robert , Bedla-Pawlusek Milena , Nowakowski Łukasz
Published: June 2019

The paper presents investigations into pool boiling heat transfer for open microchannel surfaces. The experiments were carried out with saturated FC-72 at atmospheric pressure. Parallel microchannels fabricated by machining were about 0.2 to 0.4 mm wide and 0.2 to 0.5 mm deep. Analyzed surfaces with microchannels allowed to obtain heat transfer coefficients within the range of 6.1 – 9.8 kW/m2K, which in relation to the flat surface gives a 3 – 5 - fold increase in HTC. One of the reasons for the increase in the heat transfer coefficient when increasing the heat flux was the growing number of active nucleation sites at the bottom of microchannels and its side surfaces.
Comparison of different image intensifiers used for combustion measurement
Authors: Kouba Jan , Novotný Jan , Mulenko Martin
Published: June 2019

This paper deals with setting of the acquisition equipment used to visualize and measure the concentration of intermediate species chemiluminescence combustion and laser-induced fluorescence. Observed intermediates such as OH, NO, CH and others have an emitted UV spectrum and their signal is very weak. For this reason, it is necessary to use a suitable image intensifier, and its proper setting and synchronization with the camera is also very important. In view of this problem, the following text deals with the appropriate setting of selected optical amplifiers with P46 and P43. Because the recording equipment can be used for both LIF and chemiluminescence, the experimentally determined setting will be performed using the OH-chemiluminescence method. This is reported by a weaker signal and creates a more stringent setup criterion. As a qualitative factor, a gradient of the image function has been selected, which plays a significant role in edge detection and therefore also in flame front position detection.
A thermodynamic assessment of working fluids in ORC systems
Authors: Matuszewska Dominika , Kuta Marta , Górski Jan
Published: June 2019

ORC (Organic Rankine Cycle) is widely used to convert low temperature heat into electricity using organic working fluid. The performance of an ORC installation is influenced deeply by selected working fluid and operation conditions. Recently has been presented a new generation of working fluids dedicated to ORC systems. They are characterized by near zero ODP (Ozone Depletion Potential) coefficient and significantly smaller GWP (Global Warming Potential) in comparison with currently used refrigerants. This paper presents preliminary research on selected dry and isentropic ORC fluids and some peculiarities in their behaviour.
A study of the coarse water droplets formation in the nozzle
Authors: Měšťanová Lucie , Bartoš Ondřej
Published: June 2019

The paper introduces the experimental results of the droplets formation for three different aqueous solutions. The new wind tunnel was built to study water droplets atomization from liquid films at high speed flow similar to that found in steam turbines. Liquid atomization is a widely studied problem for sprays and generally in the field of aerosol research. A similar phenomenon occurs in steam turbines but mainly with undesirable effects, the formed droplets from the film (coarse droplets) have a negative effect on the reliability and efficiency of the turbines due to the erosion and corrosion by the droplets impact on the leading edges of the blades. The new wind tunnel is equipped with classical pressure and temperature measurement systems for the determination of the initial condition in the settling chamber and measurement of the static pressure along the nozzle with a known profile. The photogrammetric method and light scattering are used to measure the diameter distribution of the droplets. The liquid film is made with an aqueous solution supplied on the symmetrical aerofoil NACA 0008. Different aqueous solutions were studied for different liquid surface tension effects.
Application of modified Navier-Stokes equations to determine the unsteady force effects of a heterogeneous liquid
Authors: Pochylý František , Klas Roman , Fialová Simona
Published: June 2019

The article is focused on calculating the force effects of a heterogeneous liquid on pipe walls. The solution is based on the concentration of solid particles. The base fluid is assumed to be incompressible. The solution will apply Euler-Lagrange's solution principle. Two tasks will be solved; with a rigid and a flexible tube wall. The solution will be carried out with non-stationary boundary conditions that were determined experimentally. Interaction of a heterogeneous fluid with a flexible wall assumes its deformation. The force effects will be solved by two methods; FSI simulation using ANSYS FEA solvers and CFD solvers ANSYS Fluent and using Navier-Stokes equations by direct integration through liquid volume. In this case, the unsteady term of the Navier-Stokes equations will be modified so that the Gauss Ostrogradsky theorem can be used to calculate the force. At the end, the force effects on the rigid and compliant wall will be compared with the unsteady turbulent flow of the heterogeneous liquid.
Mathematical simulation of temperature influence on pressure drop at pump suction line
Authors: Polášek Tomáš , Bureček Adam , Hružík Lumír
Published: June 2019

The article is focused on mathematical simulation of the temperature influence on the pressure drop at the pump suction line. It is evaluated pressure drop depending on mineral oil flow rate. The courses of individual dependencies are determined by mathematical simulation using the ANSYS CFD computing software. The temperature affects significantly physical properties of the flowing mineral oil. In a paper is also described the experimental measurement of a mineral oil sample and determination of its physical properties depending on temperature.
Selection of model liquid with refractive index matching for visualization of internal flow in a scaled atomizer model
Authors: Sapík Marcel , Malý Milan , Jedelský Jan , Wigley Graham , Cejpek Ondřej
Published: June 2019

A scaled transparent modular model of pressure-swirl (PS) atomizer was prepared from cast PMMA (Poly(methyl methacrylate), Perspex™, Plexiglas™) with the aim to achieve a better understanding of internal flow and subsequent spray formation. Because of use of high-speed imaging and Laser Doppler Anemometry (LDA) the working liquid had to be selected with respect of a refractive index matching (RIM) with the atomizer material. The liquid should be colourless and chemically non-aggressive to the model material with suitable viscosity to achieve the Reynolds number of the internal flow of the original atomizer. Froude number should be high enough to neglect the influence of gravity on the flow. An extensive search for transparent liquids and materials of enlarged models was made with a focus on RIM in performed experiments. Several liquids were chosen, and their chemical effect on PMMA was tested. Despite the successful tests that proved the liquid suit the case, the model material was damaged and the tests proved to be insufficient. For this reason, the tests were modified to better involve the stress of the bolted model. It turned out that a force effect (bolt in the thread, pre-stressed bolt connection) on the material has a significant influence on the acceleration of the chemical effect. The internal flow was examined using a high-speed camera with several liquids.
Impact of selected thermal and flow parameters on flow boiling heat transfer in a minichannel
Authors: Strąk Kinga , Piasecka Magdalena
Published: June 2019

This paper reports an impact of selected thermal and flow parameters i.e., mass flux and inlet pressure on flow boiling heat transfer in a minichannel. Research was carried out on the experimental set up with the test section fitted with a single, rectangular and vertically oriented minichannel 1.7 mm deep. Infrared thermography was used to determine changes in the temperature on the outer side of the heated minichannel wall in the central part of the minichannel. The heated element for HFE-649 flowing in the minichannel was a thin alloy plate, made of Haynes-230. Local values of heat transfer coefficient for stationary state conditions were calculated using a simple one-dimensional method. Analysis of the results was based on experimental series obtained for the same heat flux, various mass fluxes and average inlet pressures. The experimental results are presented as the relationship between the heat transfer coefficient and the distance along the minichannel length and boiling curves. The highest local heat transfer coefficients were obtained for the lower average inlet pressure and for the highest mass flux at lower heat flux.
Local velocity scaling in upward flow to tooth impeller in a fully turbulent region
Authors: Šulc Radek , Ditl Pavel , Fořt Ivan , Jašíkova Darina , Kotek Michal , Kopecký Václav , Kysela Bohuš
Published: June 2019

The hydrodynamics and flow field were measured in an agitated vessel using 2-D Time Resolved Particle Image Velocimetry (2-D TR PIV). The experiments were carried out in a fully baffled cylindrical flat bottom vessel 400 mm in inner diameter agitated by a tooth impeller 133 mm in diameter. Distilled water was used as the agitated liquid. The velocity fields were investigated in the upward flow to the impeller for three impeller rotation speeds – 300 rpm, 500 rpm and 700 rpm, corresponding to a Reynolds number in the range 94 000 < Re < 221 000. This means that fully-developed turbulent flow was reached. This Re range secures the fully-developed turbulent flow in an agitated liquid. In accordance with the theory of mixing, the dimensionless mean and fluctuation velocities in the measured directions were found to be constant and independent of the impeller Reynolds number. On the basis of the test results the spatial distributions of dimensionless velocities were calculated. The axial turbulence intensity was found to be in the majority in the range from 0.4 to 0.7, which corresponds to the middle level of turbulence intensity.
No-moving-part fluidic terminal units for control of thermal comfort in buildings (a survey)
Authors: Tesař Václav
Published: June 2019

This article surveys a so far little known approach to two simultaneously requested but mutually opposed requirements on internal conditions in buildings. It is the growing demand of better internal comfort while the other is decrease of costs and energy consumption. The internal conditions is ensured by terminal units located and adjusted at the points of conditioned air delivery into rooms. Author’s terminal units achieve the goal by having no moving parts. Advantages are low cost, robustness and long operating life without maintenance. Capability to switch the air flows at a high frequency without wear opens new ways to control, such as the flow pulse width modulation. The fast switching also makes possible small regenerative heat exchangers, keeping inside the building the heat extracted from the removed contaminated air.
About the operational determination of the state and parameters of flowing moist air
Authors: Vestfálová Magda , Šafařík Pavel
Published: June 2019

The presented paper deals with the solution of moist air parameters for the needs of aerodynamic research or design. From the thermodynamic theory of moist air, a p-t diagram of moist air is designed to allow the operative expression of the process and state of the moist air. Using this diagram, it is possible to illustratively describe the course of parameters at various state changes in moist air such as isentropic expansion and compression, isothermal expansion and compression, isobaric state change, isochoric state change, or general polytrophic state change. The initial state of moist air is determined by the pressure, temperature and moisture of the air. In the p-t diagram, the process is expressed by the applicable curve; the identification of the parameters in which the phase transformation occurs in moist air is significant. Uncertainty analysis is performed.
Lagrangian tracking of fibres in a channel flow
Authors: Volavy Jaroslav , Farkas Árpád , Lizal Frantisek , Elcner Jakub , Jicha Miroslav
Published: June 2019

Tracking of fibres in a fluid flow is much more complicated than tracking of spherical particles. In fibre motion, the orientation of fibre against the flow direction plays a very important role. In addition to the standard equation of motion, additional equations for orientation and angular velocity must be solved during the tracking of fibres. A mathematical model describing fibre motion is introduced in this work. Capabilities of this model are demonstrated through simulations of fibre transportation by air in a channel flow. The importance of the terms in the equation of angular velocity are discussed.
Blood flow in the brachial artery compressed by a cuff
Authors: Wilk Barbara , Hanus Robert
Published: June 2019

Most non-invasive blood pressure measurements are based on the blood flow during the arm cuff deflation. In this paper, the measurement system for an investigation of a blood flow in the partially occluded brachial artery is presented. It allows us to record simultaneously the cuff pressure, Korotkoff sounds and the blood flow during the arm cuff deflation. The algorithms developed for digital processing of the recorded signals are described in detail. The results of analysis obtained for healthy subjects are presented and discussed.
Modeling and Identification of the Hydraulic Servo Drive
Authors: Woś Piotr , Dindorf Ryszard
Published: June 2019

This paper discusses possibilities to apply the dynamic identification with a discrete linear model while assessing the state of the electro-hydraulic drive dynamics. This evaluation is crucial while designing modern power or positional control systems. Experimental data is applied in order to determine the model dynamics of the real system and estimate unknown parameters of an object model. The dependencies were interpreted. The paper includes the selected results of current identification tests of the electro-hydraulic drive system as a result of which the discrete parametric object model was derived.
Researches on very low frequency acoustic signal propagation characteristics in different shallow elastic wedge bottoms
Authors: Zhu Jun , Zhu Hanhao , Tang Jun , Zheng Guangxue
Published: June 2019

Targeted at the issue of extremely low-frequency (<100Hz) acoustic propagation in complex shallow elastic bottom environments. The influence law of different complex elastic bottoms on the acoustic signal propagation at very low frequency by acoustic energy flux has been analyzed with the simulation, which is based on the finite element method. The elastic bottoms which have been studied are the shallow horizontal elastic bottom, and the up-sloping and the down-sloping elastic bottom. The results show that the acoustic signal propagating in the up-sloping and down-sloping elastic bottom environments is more complex than that propagating in the horizontal elastic bottom, and the acoustic energy leaking into those elastic bottoms has very different influence on the acoustic signal propagation, especially in the up-sloping bottom.
Study on Doppler characteristics of underwater bistatic reverberation
Authors: Wang Fangyong , Jiang Yeming , Du Shuanping
Published: June 2019

Active sonar has two typical types of geometry configuration respectively named monostatic and bistatic like a radar system. In the monostatic scenario, co-located underwater transducers transmit and receive sound energy, while in a bistatic situation the transducers are physically separated. Both object detection and identification can be significantly enhanced through utilization of the additional dimension provided by a bistatic geometry. So, more people care about bistatic scattering characteristics of underwater objects as well as bistatic reverberation in recent years. In this paper, Doppler characteristics of bistatic reverberation generated by moving transmitter and receiver are studied. Theoretical formulism for receiving frequency of bistatic reverberation is derived in case of a tone signal being transmitted. Further analysis shows bistatic reverberation is more complicated than monostatic reverberation when Doppler is concerned. In monostatic case, the Doppler frequency shift of reverberation relates to centre frequency of the tone signal, velocity of the transmitter as well as the arriving direction. While in bistatic situation, it varies not only with the above factors, but also the locations, moving directions, velocities of both transmitter and receiver, and also the arriving time of the reverberation, which makes extraction and utilization of Doppler information more difficult.
A fast algorithm to compute shadow areas for Kirchhoff approximation-based underwater acoustic scattering simulation
Authors: Jia Lianhui , Zhang Yang , Li Guijuan
Published: June 2019

Kirchhoff approximation method is a fast underwater acoustic scattering numerical method which adaptive to engineering application. Shadow areas calculation is one of the most important factors for computational efficiency. In this paper, several existing shadow domain calculation methods for underwater acoustic numerical simulation based on Kirchhoff approximation are introduced. On this basis, a fast sheltering method based on the linked-list search algorithm is proposed. Linked-list search algorithm uses element geometric center to express the element space position and projects the geometric center on incident wave plane along the incident sound ray. And linked-list relationship of elements is established by dividing background mesh cell on the screen. The algorithm achieves fast calculation by using linked-list relationship and optimizing the calculation path. Linked-list search algorithm and all-pair search algorithm are compared and analyzed by an example of numerical simulation. The computational efficiency of the fast shadow domain algorithm is verified by comparing the results of the two algorithms. And the suggestions for further improving the computational efficiency of the algorithm are proposed.
Acoustic source localization using the open spherical microphone array in the low-frequency range
Authors: Yang Boquan , Shi Shengguo , Yang Desen
Published: June 2019

Recently, spherical microphone arrays (SMA) have become increasingly significant for source localization and identification in three dimension due to its spherical symmetry. However, conventional Spherical Harmonic Beamforming (SHB) based on SMA has limitations, such as poor resolution and high side-lobe levels in image maps. To overcome these limitations, this paper employs the iterative generalized inverse beamforming algorithm with a virtual extrapolated open spherical microphone array. The sidelobes can be suppressed and the main-lobe can be narrowed by introducing the two iteration processes into the generalized inverse beamforming (GIB) algorithm. The instability caused by uncertainties in actual measurements, such as measurement noise and configuration problems in the process of GIB, can be minimized by iteratively redefining the form of regularization matrix and the corresponding GIB localization results. In addition, the poor performance of microphone arrays in the low-frequency range due to the array aperture can be improved by using a virtual extrapolated open spherical array (EA), which has a larger array aperture. The virtual array is obtained by a kind of data preprocessing method through the regularization matrix algorithm. Both results from simulations and experiments show the feasibility and accuracy of the method.
Numerical study of dynamic noseleaf models in greater horseshoe bats, Rhinolophus ferrumequinum
Authors: Gao Li , Lu Hongwang , Feng Jianxiong , Zhang Zhiwei , Ma Xin , He Weikai
Published: June 2019

Echolocating greater horseshoe bats (Rhinolophus ferrumequinum) emit biosonar pulses through nostril. The nostrilis surrounded by sophisticated and delicate appendages, i.e. noseleaf. It is known that the static part of noseleaf can cause different effects on bat biosonar pulse. In addition, the dynmaic noseleaf was found to be able to shape their emission beam. For detailed investigation of the effects of dynamic lancet on the ultrasonic beam, a 3D noseleaf model was constructed using the micro CT scanning of the noseleaf samples, and a simple model was constructed digitally for comparison. The model consists of two parts, for which one is the triangle on the top and the other one is the rectangle at the bottom. Quantitative numerical investigation on the lancet dynamic effect on the ultrasonic beam was performed using finite element analysis for both models.
Underwater target recognition method based on convolution residual network
Authors: Chen Yuechao , Du Shuanping , Quan HengHeng , Zhou Bin
Published: June 2019

The underwater target radiated noises usually have characteristics of low signal to noise ratio, complex signal components and so on. Therefore the recognition is a difficult task and powerful recognition method must be applied to obtain good results. In this paper, a recognition method for underwater target radiated noise time-frequency image based on convolutional neural network with residual units is proposed. The principles and characteristics of the convolutional residual network are analyzed and three basic convolutional residual units are put forward. Then three convolutional residual network models with very deep structure are established based on basic convolutional residual units and some normal convolution layers. The number of the hidden layers is 50, 100 and 150 respectively and softmax algorithm is used as the top classifier. The wavelet transform is adopted to generate time-frequency images of the underwater target radiated noises with frequency band of 10~200Hz, thus ensuring the accuracy of local structure of the image, then the above three models can be used to recognize the images. The experimental data of two types of targets were processed. The results are as follows. As the number of training time increases, the training loss shows a convergence trend and the recognition accuracy of test data gradually increases to more than 90%. In addition, the top-level output has obvious separability. The final recognition accuracies of the three convolutional residual networks are all over 93% and higher than that of normal convolutional neural network with 5 layers. As the number of layers increases, the recognition accuracy of the convolutional residual network increases to a certain extent, illustrating the increase of layer number can improve the processing effect. The analysis results show that the convolution residual network can extract features with separability through deep structure and achieve effective underwater target recognition.
Design of an underwater acoustic array for full ocean depth multi-beam echo sounder
Authors: Hao Haoqi , Xia Tiejian , Xie Min
Published: June 2019

In order to meet the technical requirements of full ocean depth multibeam echo sounder, the underwater acoustic array must have the ability of wide coverage, broadband response, high sensitivity and high reliability. This paper presents a design of underwater acoustic array based on Mills cross configuration with separate transmitting and receiving units. The arrays have modules design, hence the beamwidth of the array can be adjusted according to particular installation requirements. The working frequency band of the arrays is between 10.5kHz to 13.5kHz, and the coverage angle can cover -71.6°~71.6°. The Integrated design is used to achieve a wide-angle beam coverage of the planar array, which combines the transducer and the sound baffle together to realize a wide directivity of the array elements. The longitudinal bending transducers are designed to meet the broadband requirements for the transmitting array, which are Tonpilz transducers with flexural radiating head. On the other hand, each element of the receiving array is composed of several hydrophones, which are connected in series to achieve high sensitivity. The double-layer watertight technology is also applied in our design, ensuring stable performance and long service life.