bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensor scheduling for electronic support to intercept beam‐agile radar
Authors: Clarkson I. Vaughan L.
Published: June 2019

Modern electronically scanned‐array radars can switch between beams in a matter of microseconds. This allows great latitude in constructing the beam schedule. From the point of view of an electronic support (ES) receiver, what are the implications? Repeated search tends to make the radar's beam schedule more regular and predictable. Can this be exploited by the receiver to intercept the radar more quickly? What can be done about strongly aperiodic beam schedules? In this study, the author proposes two opposing models for a beam‐agile radar. One is a periodic model, accounting for radars with a predictable, repetitive search operation. The other is a stochastic model, in which the beam schedule is modelled by a continuous‐time Markov chain, accounting for strongly aperiodic radars. Taking the published beam schedule of a hypothetical, agile radar, numerical experiments are conducted under two different assumptions about the ordering of beam dwells in each radar scan. Under the assumption that the dwells are sequentially ordered, it is found that the beam schedule appears periodic from the receiver's point of view, to a good approximation. On the other hand, when the radar dwells are randomly shuffled on each scan, the Markov‐chain model proves useful in guiding receiver settings.
Task‐scheduling scheme based on greedy algorithm in integrated radar and communication systems
Authors: Huang Ling , Zhang Yu , Li Qingyu , Pan Changyong , Song Jian
Published: June 2019

Integrated radar and communication system can significantly enhance the work efficiency and considerably occupy less hardware resources. However, the integrated systems have limited supply resources, where a proper scheduling scheme is needed to meet the requirement of systems. Here, the authors propose a task‐scheduling scheme based on the greedy algorithm, where each arrangement is the result of selecting the minimum shift time compared with the expected time. By guaranteeing the best result of each task, the minimum average time shift ratio (ATSR) of the whole tasks is obtained. Simulation results show that when the number of the tasks is quite large, the proposed scheme has more advantages than the traditional scheme based on time pointer algorithm. Authors’ proposed scheme can significantly reduce the average offset time of tasks while maintaining a satisfactory successful scheduling rate (SSR), which shows more advantages in the integrated systems.
Flow pattern of accelerated cometary ions inside and outside the diamagnetic cavity of comet 67P/Churyumov-Gerasimenko
Authors: Masunaga K. , Nilsson H. , Behar E. , Stenberg Wieser G. , Wieser M. , Goetz C.
Published: June 2019

Analyzing data from the Ion Composition Analyzer on board the Rosetta spacecraft, we studied a flow pattern of accelerated cometary ions (40–80 eV) inside and outside the diamagnetic cavity of comet 67P/Churyumov-Gerasimenko (67P). We found that the accelerated ions are intermittently observed and are ten times more frequently observed outside the cavity than inside, and they mainly flow tailward with an aberration (~20–40°). We suggest that they are accelerated by the tailward polarization electric field upstream of the comet. Because their occurrence frequency becomes lowest near perihelion where the water production rate is highest at 67P, ion-neutral collisions and/or charge exchange may play a role in controlling the occurrence frequency. The aberration pattern is different inside and outside the cavity in the cometocentric solar equatorial (CSEQ) frame but it is consistent in the comet-Sun electric (CSE) frame; the latter is rotated from the CSEQ frame about the comet-Sun line so that theZ-axis is aligned with the local motional electric field. Because the flow pattern of the accelerated ions inside the cavity in the CSE frame is the same as outside, we suggest that the flow pattern inside is determined by the flow outside, depending on the local plasma and magnetic field. Near the CSE polar plane the aberration is in the opposite direction of the motional electric field, while it is in the anti-cometward direction near the CSE equator plane. The aberration in the anti-electric-field direction near the CSE polar plane suggests that the accelerated ions are mass-loaded by local cold cometary ions, just like the mass-loading of the solar wind by cold cometary ions. The cause of the anti-cometward aberration near the CSE equator plane is still unknown, but this may indicate that the tailward-flowing cometary ions are deflected across the upstream boundaries or by an outward-pointing ambipolar electric field.
Imaging the molecular interstellar medium in a gravitationally lensed star-forming galaxy at z = 5.7
Authors: Apostolovski Yordanka , Aravena Manuel , Anguita Timo , Spilker Justin , Weiß Axel , Béthermin Matthieu , Chapman Scott C. , Chen Chian-Chou , Cunningham Daniel , De Breuck Carlos , Dong Chenxing , Hayward Christopher C. , Hezaveh Yashar , Jarugula Sreevani , Litke Katrina , Ma Jingzhe , Marrone Daniel P. , Narayanan Desika , Reuter Cassie A. , Rotermund Kaja , Vieira Joaquin
Published: June 2019

Aims. We present and study spatially resolved imaging obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) of multiple 12CO(J = 6 − 5, 8−7, and 9−8) and two H2O(202−111 and 211−202) emission lines and cold dust continuum toward the gravitationally lensed dusty star-forming galaxy SPT 0346-52 at z = 5.656.

Methods. Using a visibility-domain source-plane reconstruction we probe the structure and dynamics of the different components of the interstellar medium (ISM) in this galaxy down to scales of 1 kpc in the source plane.

Results. Measurements of the intrinsic sizes of the different CO emission lines indicate that the higher J transitions trace more compact regions in the galaxy. Similarly, we find smaller dust continuum intrinsic sizes with decreasing wavelength, based on observations at rest frame 130, 300, and 450 μm. The source shows significant velocity structure, and clear asymmetry where an elongated structure is observed in the source plane with significant variations in their reconstructed sizes. This could be attributed to a compact merger or turbulent disk rotation. The differences in velocity structure through the different line tracers, however, hint at the former scenario in agreement with previous [CII] line imaging results. Measurements of the CO line ratios and magnifications yield significant variations as a function of velocity, suggesting that modeling of the ISM using integrated values could be misinterpreted. Modeling of the ISM in SPT 0346-52 based on delensed fluxes indicates a highly dense and warm medium, qualitatively similar to that observed in high-redshift quasar hosts.
Effect of the blade number on the marine propeller performance
Authors: Bouregba Fatima , Belkadi Mustapha , Aounallah Mohammed , Adjlout Lahouari
Published: June 2019

This paper deals with numerical simulation of stationary flow around a marine propeller. The aim is to reproduce the hydrodynamic turbulent flow around the Wageningen B serie propellers in open water using the ANSYS FLUENT code and the RANS approach. The computational domain consists of an inter-blade channel with periodic boundaries, meshed with tetrahedral cells. The turbulence is modeled with the k-ω. The obtained results provide good agreement with the available experimental data and show that the blades number affects considerably the marine propellers performances. It is interesting to notice that the six blades propeller is the best adapted one for the open water flows.
Similarity of temperature and concentration field in Poiseuille–Benard channel flow
Authors: Devera Jakub , Hyhlík Tomáš , Kalinay Radomír
Published: June 2019

A flow over hot water film in horizontal channel (Poiseuille–Benard flow) is studied experimentally and by means of CFD. Averaged temperature and concentration fields were measured in central transverse plane using RTD and capacitive humidity probe for different Ri = Gr/Re2. A similarity of thermal and concentration field is discussed and the influence of thermal and humidity field by radiative heat transfer is investigated since it has a considerable effect. Same cases are modeled by CFD in commercial code Star-CCM+. Simulated thermal and concentration fields shows similar character as those from measurements when radiative heat transfer mode is considered.
Hydrodynamic education with rheoscopic fluid
Authors: Duda Daniel , Klimko Marek , Škach Radek , Uher Jan , Uruba Václav
Published: June 2019

We present a educational poster supporting the subject „Mechanics of fluids I“, which the students evaluate to be diﬃcult mainly due to abstractness. Our goal is to show in vivo the behavior, especially the non-linearity, of various flows transiting into turbulence. The fluid motion is visualized by using the rheoscopic fluid, which consist of water and the dust of mica, whose particles are longitudinal and shiny resulting into easily observable reflections, when the particles coherently orient along the maximum stress. This happens mainly in shear layers, e.g. at the boundary between vortex core and envelope. An example of flow transiting into turbulence is the Taylor-Couette flow between two concentric cylinders, which with increasing Taylor number passes through various regimes from fully laminar bearing flow through the Taylor vortex flow (TVF) and later Wavy vortex flow (WVF) up to Turbulent Taylor vortices regime (TTV) and, finally, the regime of featureless turbulence.
A new form of equation for force determination based on Navier-Stokes equations
Authors: Fialová Simona , Pochylý František , Šedivý Dominik
Published: June 2019

This work is focused on calculating the force effects of an incompressible homogeneous liquid on a surface of a rigid or a flexible tube. An unsteady flow induced by differential pressure at the beginning and at the end of the tube is assumed. The pressure difference for the unsteady flow is determined experimentally. The mathematical model is based on modified Navier-Stokes equations. The unsteady term is modified in order to be able to use the Gauss-Ostrogradsky theorem to calculate the force. This method of solution will allow the calculation of the force by integration of the Navier-Stokes equations, which will help to refine and simplify the calculations. In the article, both methods of force calculation will be presented and compared both through the ANSYS FEA and CFD ANSYS Fluent solvers and by the integration of the Navier-Stokes equation. The calculation will not only respect the compliance of the tube but also its movement status.
Determination of the uncertainty of mass flow measurement using the orifice for different values of the Reynolds number
Authors: Golijanek-Jędrzejczyk Anna , Mrowiec Andrzej , Hanus Robert , Zych Marcin , Świsulski Dariusz
Published: June 2019

Standard orifice flowmeters are widely used in the chemical and energy industry. Therefore, it is essential to know how accurate the measurements made with these instruments are. The paper presents an estimation of measurement uncertainty of a liquid mass flow using the orifice plate. The authors will present the influence of ranges of the Reynolds number on the estimated uncertainty, obtained on the basis of simulation and laboratory experiments. The research was conducted for the central orifice in the Reynolds number 8,000 < Re < 21,000. The results of estimating the extended uncertainty of the measurement of water flow using simulation and experimental method, are convergent. The maximum difference in the extended uncertainty values of flow measurement for the simulation and experiment was 0.04.10-3 kg/s.
Progress in design of adsorption refrigeration systems. Evaporators
Authors: Kalawa Wojciech , Grabowska Karolina , Sztekler Karol , Krzywański Jarosław , Sosnowski Marcin , Stefański Sebastian , Siwek Tomasz , Nowak Wojciech
Published: June 2019

Adsorption heat pumps are becoming increasingly popular. Due to their design, they enable application of low-temperature heat sources. Evaporators for adsorption chillers make one of the basic design elements determining the correct operation of these devices. The specificity of operation in low pressures and temperatures is the reason why their design significantly differs from that of conventional evaporators. The pluralities of existing solutions as well as the lack of a systematic review of them cause difficulties in correct evaluation and choice of design. The paper presents the current state of art as well as a review of the existing solutions of evaporators used in adsorption heat pumps. The purpose of the review research is to present various solutions of evaporators as well as indicating their advantages and disadvantages in order facilitate the choice of the optimal design.
Pool boiling visualization of Novec-649 and FC-72 on copper microchannels
Authors: Kaniowski Robert , Pastuszko Robert
Published: June 2019

Saturated pool boiling from copper microchannel surfaces was examined using Novec-649 and FC-72 as working fluids. Parallel microchannels fabricated by machining were about 0.2 mm wide, and 0.2 to 0.4 mm deep and spaced every 0.4 mm. The experiments were carried out at atmospheric pressure. The images of the growing and departing bubbles for the entire surface of the specimen were taken with a Photonfocus PHOT MV-D1024-160-CL camera and an EX-FH20 (Casio) camera. At low superheats, the bubbles departing from enhanced surfaces were spherical in shape and did not coalesce. At higher superheats, the bubbles interacted with each other intensively, forming flattened spherical, funnel-shaped bubbles at the bottom. The visualization study aimed at identifying nucleation sites of the departing bubbles and determining their diameters and frequency at various superheats.
The influence of the conversion medium stream on the gasification process of olive pits
Authors: Król Danuta , Poskrobko Sławomir
Published: June 2019

The paper presents the results of research on gasification of olive pits and production of a generator gas with calorific value enabling its combustion in microturbines. Gasification was carried out in a laboratory gasification reactor, where the converting factor was air. The influence of the flow rate of its stream on the composition of the generator gas was investigated. The research involved searching for optimal process conditions for gasification of this biomass, to obtain a generator gas with an increased CH4 content (methane is the most calorific component).The air flow in subsequent tests was 0.5m3/h, 0.85m3 /h, 1.1m3/h,. 1.4m3/h 1.7m3/h. The quantitative composition of the generated generator gases differed. These conditions were obtained with an air flow of 1.4m3/h, in a tubular reactor, at the bed temperature T3= 456–462oC. A gas was obtained, with a calorific value of 9.2MJ/m3, characteristic for the following gas composition: H2=3.88%, CO=18.52%, CO2=6.27%, CH4=16.02%, O2=1.28%.
Some Peculiarities of Helicopter Main Rotor Aeroacoustic for Far-Field Observer
Authors: Kusyumov Alexander , Mikhailov Sergey , Kusyumov Sergey , Romanova Elena , Barakos Georgios
Published: June 2019

Mathematical models for helicopter rotor acoustics are usually based on the Ffowcs Williams–Hawkings (FW–H) equation. The level of rotor noise is determined by geometry (thickness noise) of a flying vehicle and distributed blade loading (loading noise). Initially, the FW-H equation was obtained from Euler’s equations and does not depend on the viscosity of flow. In the present work the UH-1H helicopter is considered as a test case for numerical CFD simulation and comparison to experimental data.
Maximization of performance of a PCM – based thermal energy storage systems
Authors: Kuta Marta , Matuszewska Dominika , Wójcik Tadeusz M.
Published: June 2019

Phase change materials (PCMs) are significant in terms of applicability for the thermal energy storage (TES). Thanks to the high thermal storage density and wide range of phase transition temperature they are promising storage mediums for a large number of applications. PCMs can be used to support efficient use of waste or excess heat. Selection of adequate material as well as design of optimal TES magazine are crucial. It is important to choose material which is characterized by suitable temperature range of phase transition, possibly high latent heat of transition, specific heat and thermal conductivity. Also important features are: ability to work properly after many operation cycles, minimum volume change and gas generation during the phase transition. It is also advantageous when PCM is non-toxic and non-corrosive, non-flammable, non-explosive, environment friendly and easy to recycle. Even the best designed PCMs would not be able to store heat efficiently if the whole magazine and its construction were not good enough. This is the reason why a lot of effort is taken to design effective TES system. The aim of this work is to analyse examples of different configurations of PCM – based thermal energy storage systems. Authors compare selected TES systems and discuss their characteristics.
The simulation of the gas flow through the porous media and fences
Authors: Kyncl Martin , Pelant Jaroslav
Published: June 2019

The paper is focused on the numerical simulation of the compressible gas flow through the porous media and fences. We work with the the non-stationary viscous compressible fluid flow, described by the RANS equations. The flow through the porous media is characterized by the loss of momentum. It is possible to use various methods for the simulation of such flow. Here we present the approach with the modification of the source term, and other possibilities using the modification of the face flux. The original approach was presented recently by the authors analysing the modification of the Riemann problem with one-side initial condition, complemented with the Darcy’s law and added inertial loss. Another aim of this paper is the evaluation and estimate of the forces acting on the diﬀusible barrier (fence) with given parameters. The presented examples were obtained with the own-developed code for the solution of the compressible gas flow.
Estimating uncertainty of temperature measurements for studies of flow boiling heat transfer in minichannels
Authors: Michalski Dariusz , Strąk Kinga , Piasecka Magdalena
Published: June 2019

This paper presents the method of estimating the uncertainty of temperature measurements conducted using K-type thermocouples in the study of flow boiling heat transfer in minichannels. During heat transfer experiments. the fluid temperature at the inlet and outlet of the minichannel is measured with thermocouples connected to a DaqLab 2005 data acquisition station. The major part of the experimental setup for calibration of temperature measurement included a calibrator of thermocouples. The thermocouples were manufactured by Czaki Thermo-Product. Poland. The temperatures recorded with the thermocouples were compared statistically while measuring the temperature of demineralised water at several characteristic points at liquid phase change or using the reference temperature known from the calibrator. The experimental error of the temperature measurement method was determined according to the principles of statistical analysis. Estimates of the mean value and the experimental standard deviation of the experimental error as well as the confidence interval for a single experimental error and the measurement accuracy were presented. The uncertainty of the difference in temperature was also calculated
The effect of blade slots on flow behaviour in a fan impeller
Authors: Pieruszka Adam , Siwek Tomasz , Kalawa Wojciech , Lis Łukasz , Stefański Sebastian , Sztekler Karol
Published: June 2019

The use of blade slots is one of the passive methods of controlling flow in a fan impeller. Numerical CFD analyses indicate a possibility of controlling the point of flow separation in the inter-blade space depending on various configurations of the aperture arrangement. Bench studies confirm the possibility of changing the increase of total pressure and internal efficiency. Additionally, the changes affect the noise level during fan operation.
Registration of high-frequency waves on the surface by the interference methods
Authors: Shmyrova Anastasia , Shmyrov Andrey , Mizeva Irina , Mizev Alexey
Published: June 2019

Capillary waves are frequently used to measure the surface tension of liquids. However, this approach has not found wide application in the manufacture of modern commercial tensiometers because of the limitations imposed by capillary wave excitation techniques and the labor input associated with its practical implementation. In this paper we introduce a modified version of the capillary wave method which allows one to avoid the existing limitations and disadvantages. The distinguishing features of the proposed technique are as follows: acoustic wave generation and application of an interferometry technique for 3D surface profile reconstruction. A dynamic speaker with controlled vibration frequency and amplitude is used to produce acoustic vibrations. Application of a conventional Fizeau interferometer and the spatial phase shifting method makes it possible to perform surface form measurements with a high accuracy. For calculating wavelengths and the damping co-efficient, the surface profile is fitted with a decaying cylindrical wave equation. The accuracy of surface tension measurement by the modified capillary wave technique is 0.3 %. Owing to the non-contact way of wave generation and the small amounts of the examined fluid, the proposed method can be used in different studies.
Bypass Boundary Layer Transition on Flat Plate by Adverse Pressure Gradient
Authors: Skála Vladislav , Uruba Václav , Antoš Pavel , Jonáš Pavel
Published: June 2019

Bypass boundary layer transition in flows on flat plate by adverse pressure gradient was investigated experimentally. It was measuered cases with combination of adverse pressure gradient by different free stream turbulence intenzity. Hot wire anemometry technique was used. Measuerement were made on flat plate in closed wind tunnel. Adverse pressure gradient was set by diffuser in tested section of wind tunnel. Grid turbulence of free stream was controlled by screen. Hot wire anemometry technique was used, intermitency factor was evaluated. Results were compared wih cases with simpliest conditions.
Numerical Investigation of the Hub-Seal Mass Flow Rate Effect on the Axial Turbine Stage Efficiency
Authors: Straka Petr
Published: June 2019

The contribution deals with numerical simulation of compressible flow through the axial turbine stage equipped with the hub-seal. The current flowing from the hub-seal has a major impact on the secondary flow in the hub-region of the blade span. The aim of this work is to found a dependency of the efficiency-drop on the hub-seal mass flow rate. Numerical simulation has been made for configuration of experimental axial single-stage reaction turbine.
Test section of the wind tunnel IT for aeroelastic experiments with blade cascades
Authors: Vlček Václav , Procházka Pavel
Published: June 2019

The article presents the way how the existing small vacuum aerodynamic tunnel IT (Institute of Thermomechanics) has been adapted for the measurement of the aeroelastic properties of the NACA 0015 airfoil and of the blade cascades composed of various types of blades with two degrees of freedom, pitch and common plunge. Attention was focused on the possibility of studying self-excited vibration at lower subsonic speeds. The modification of the test section is based on the knowledge gained during the study of self-excited airfoil oscillation.
Computational sound field in a virtual environment via field data in an arbitrary real environment
Authors: Li Xiaolei , Gao Dazhi , Wang Ning
Published: June 2019

It is useful to compute sound field of a source in a virtual environment which is different from the measurement environment. For example, some properties of sound source, such as directivity index and frequency response curve, are required to be measured in an anechoic room or free space, but both of them cannot be always accessible. Consequently, it will be useful to compute sound field of a source in free space when sound field of the source is not measured in the free space. In the aforementioned example, the free space is a virtual environment. Based on reciprocity theorem and modal expansion, a method to predict sound field of a source in a virtual environment is given in this paper when the scattering effect of the source can be neglected. Reciprocity theorem builds the relationship between measured sound field and predicted sound field, which plays an important role in the method. Green’s function in the virtual environment is needed in the method. To restrict measurement points on an enclosed surface, the Green’s function is expanded by a set of modes. A simulation is given to examine the validity of the method.
Low frequency absolute calibration of complex sensitivity of vector receivers in free-field
Authors: Jia Guanghui , Chen Yi , Ping Zihong , Fei Teng
Published: June 2019

Three-transducers spherical wave reciprocity method in free-field is demonstrated effectively for absolute calibration of the complex sensitivity of underwater sound pressure gradient of vector receiver in the frequency range 250 Hz to 4 kHz. The regularity of underwater sound pressure gradient distribution in the spherical wave, the theory of three-transducers reciprocity calibration method and the technique of complex moving weighted average (CMWA) are studied and reviewed. The VHS90 vector receiver manufactured by Hangzhou Applied Acoustics Research Institute (HAARI) is calibrated using underwater sound pressure gradient calibration facility in a 50 m×15 m×10 m anechoic tank. To verify the results of measurements, the VHS90 vector receiver is also calibrated using low frequency vector receiver calibration facility and the underwater sound pressure calibration facility. The calibration results and the comparisons with these facilities prove the accuracy of the calibration method and facilities described in this paper. The max deviation of modulus of complex sensitivity is 0.7 dB and max deviation of phase congruency of three channels is 1.6°.
Modelling, measurement and optimization of self-noise of hydrophone with preamplifier
Authors: Chen Yi , Zhou Lisheng , Guo Xiyang , He Tao , Zhang Jun
Published: June 2019

Self-noise is an important specification of hydrophone with preamplifier. This paper presents the modelling, measurement and optimization of the self-noise of hydrophone with preamplifier. Through analyzing various noise sources of hydrophone and its preamplifier, an effective self-noise model of hydrophone with preamplifier was established, and the self-noise was mainly affected by the hydrophone quality factor, preamplifier noise and thermal noise of preamplifier input resistance. In order to measure the self-noise of hydrophone with preamplifier, a measurement system was constructed and used for measuring the self-noise of a RHSA30 hydrophone which manufactured by Hangzhou Applied Acoustics Research Institute (HAARI) and has a typical sensitivity of -173 dB. After optimization of the self-noise of RHSA30 hydrophone, the measured equivalent noise pressure spectral density level was close to 30 dB at the frequency of 1000 Hz. The measurement results proved that the preamplifier current noise which mainly coming from the Operational Amplifier played a leading role at low frequencies of hydrophone with preamplifier. And some basic principles for self-noise optimization of hydrophone with preamplifier were given at the end.
Nonparametric and parametric methods of spectral analysis
Authors: Zhao Hangfang , Gui Lin
Published: June 2019

Spectral Analysis is one of the most important methods in signal processing. In practical application, it is critical to discuss the power spectral density estimation of finite data sampled from some stationary time series. A spectral estimator is expected to have good statistical properties such as consistency, high resolution and small variance. For one spectral estimation method, there exists a trade-off between high resolution and small variance. The paper provides a comparison of several popular spectral methods from both theoretical properties and practical applications. We first address several basic nonparametric methods, whose statistical characters are analysed. Then we explain the connections and differences between temporal windowing and lag windowing. Thereafter, the confidence intervals of both windows are given and used to evaluate the estimated results. Besides, several different parametric estimation methods of autoregressive time series are compared, and whose properties and effects are also introduced. Building on our understanding of these studies, we then apply parametric and nonparametric spectral estimation methods on the data of ocean surface wave height.
Theoretical and experimental study on a finite size vector sensor array with a cylindrically symmetric carrier
Authors: Guo Junyuan , Yang Shi-e , Chen Hongjuan , Piao Shengchun , Qiu Longhao
Published: June 2019

In this work, a finite size acoustic vector sensor (AVS) array is designed and its performance is theoretically and experimentally studied. The two-dimensional AVS array is comprised of five vector sensors and configured as a cross, and the array carrier is a cylindrically symmetric structure. Theoretical analysis and simulation indicate that the proposed method considering structure scattering can widen the working bandwidth. Furthermore, the utilization of vector sensor enables a significant white noise gain improvement at low frequencies, which makes the array more robust and easier to realize. Experiments have been done to study the array performance from several aspects including sensor noise characteristics, the beampattern, the direction-of-arrival (DOA) estimation ability and the array gain. From the change of the sensor directivity patterns or the amplitude distortion of the noise field, we can clearly observe the scattering field intensity. Moreover, it shows that the influence of the structure scattering on the tangential component of the vector field is symmetric, while that of the radial component is asymmetric. Experimental results also demonstrate that, with the proposed method, the 2nd and the 3rd order beamformers can be obtained which could be further used for the estimation of target DOA. In addition, an array gain of at least 6 dB is obtained capable of detection of weak signals. Our results indicate that the proposed array with a physical size less than one meter, although affected by nearby scatterers, can effectively break the Rayleigh limit and realize the remote detection in low-frequency regime.
Prediction of flow noise around a cylinder based on Large-Eddy Simulation and acoustic analogy method
Authors: Qin Qikai , Shang Dejiang , Liu Yongwei , Wang Tianyu
Published: June 2019

In this article, a hybrid method combining large eddy simulation with acoustic analogy is presented to predict three-dimensional far field noise induced by flow around a cylinder. Firstly, the governing equation including RANS equations with shear-stress transport (SST) k-ω turbulent model is numerically solved for steady flow field by using Ansys Fluent. Transient flow field is numerically solved by LES. Then, the flow field simulation results are used to compute the flow-induced noise with the FW-H integral equation method and BEM method based on Lighthill acoustic analogy equation in Actran. Before using for flow around a cylinder, accuracy of flow turbulent model in predicting turbulent flow around a cylinder is tested by comparing with available experimental data. According on the simulation result, the characteristic of the acoustic field, noise at some special points in frequency domain, the noise radiation directivity are studied. Analysis of noise distribution and frequency spectrum curves shows that dipole source takes the dominant place in the noise around a cylinder under the conditions of this article. The flow noise around a cylinder is mainly concentrated in the low frequency range.
Underwater radiated noise from commercial ships in the Yellow Sea of China
Authors: Jiang Pengfei , Lin Jianheng , Sun Junping , Yi Xuejuan
Published: June 2019

During the past decades, ship-building and engine-manufacturing have developed very quickly. The source levels of modern ships may have changed. The underwater radiated noise from many commercial ships of opportunity was measured by bottom-mounted self-contained hydrophone near the shipping lanes in the yellow sea of China one day in each month from June. 2014 to Mar. 2016. Twenty seven ships among them are selected whose peak value of 20-1000Hz passing curve is 10dB higher than background noise level. A Gaussian source distribution in depth direction is supposed and source levels normalized at different ranges are averaged in source levels acquisition to reduce the error of transmission loss calculation. A key result was the estimated results of RANDI-3 are much greater than measured results universally for ships whose length are larger than 200 meters, however, the two are close for ships whose length are less than 150 meters. Furthermore, the samples were divided into two categories to analyze. The broad-band source levels of modern commercial ships are not highly correlated to ship length but closely related to ship speed. The decay slope is less than RANDI-3.
Microstructural, mechanical and corrosion properties of dissimilar joint between AISI A321 stainless steel and ASTM A537CL1 structural steel produced by GTAW process
Authors: Sadeghi Behnam , Sharifi Hassan , Rafiei Mahdi , Abbasian Ahmad Reza , Saebnoori Ehsan
Published: June 2019

In this research, the microstructural, mechanical and corrosion properties of the dissimilar joint of ASTM A537CL1 to AISI A321 steels produced by GTAW process were studied. The welding process was done with ER308L filler metal without pre and post weld heat treatment. The scanning electron microscope and optical microscope were used to study the microstructure and fracture surface of the welded samples. Also, the mechanical behavior of the joint was evaluated by impact, tensile, bending and microhardness tests. The results illustrated that the microstructure of the weld metal was austenite with dendritic structure contained skeletal and lathy ferrite. In tension tests, all weldments failed from A537 base metal. The results of impact test indicated that all specimens exhibit ductile fracture and indicated high impact energy of about 205 J. In fine grain HAZ of A537 steel, because of formation of fine equiaxed grains due to the allotropic transformation, high microhardness was seen. While, in coarse grain HAZ, due to the formation of bigger grains, carbon migration and decreasing in the amount of pearlite phase, the microhardness slightly decreased. The exsistence of chromium in microstructure improved the corrosion resistance and the weld metal indicated acceptable corrosion resistance as compared with both base metals.
Plant Specialized Metabolites in Hazelnut (Corylus avellana) Kernel and Byproducts: An Update on Chemistry, Biological Activity, and Analytical Aspects
Authors: Bottone Alfredo , Cerulli Antonietta , DʼUrso Gilda , Masullo Milena , Montoro Paola , Napolitano Assunta , Piacente Sonia
Published: June 2019

Corylus avellana (hazelnut) is one of the most popular tree nuts on a worldwide basis. The main products of C. avellana are kernels, a nutritious food, with a high content of healthy lipids, contained in a hard shell. In recent years, along with the ongoing research carried out on hazelnut kernels, a growing interest has been addressed to the hazelnut byproducts including hazelnut skin, hazelnut hard shell, and hazelnut green leafy cover as well as hazelnut tree leaf. These byproducts deriving from the roasting, cracking, shelling/hulling, and harvesting processes have been found as a source of “phytochemicals” with biological activity. The aim of this review is to provide a comprehensive and critical update on the chemistry and biological activity of specialized metabolites occurring in hazelnut kernels and byproducts. Phenolics are the most abundant phytochemicals not only in the kernels, but also in other processing byproducts. Attention has been also devoted to taxane derivatives isolated from C. avellana leaves. An overview on the biological activity, mainly antioxidant, antiproliferative, and antimicrobial along with less common biological effects, has been provided, contributing to highlight C. avellana as a source of bioactive phytochemicals with the potential to exert beneficial effects on human health. Finally, analytical techniques for the quali-quantitative analysis of specialized metabolites occurring in the different parts of C. avellana have been reviewed.
Structural Characterization and Anti-complementary Activities of Two Polysaccharides from Houttuynia cordata
Authors: Lu Yan , Zhang Juan-Juan , Huo Jiang-Yan , Chen Dao-Feng
Published: June 2019

In previous studies, crude Houttuynia cordata polysaccharides showed beneficial effects on acute lung injury in vivo, a syndrome in which anti-complementary activities played an important role. Anti-complementary activity-guided fractionation of H. cordata polysaccharides led to the isolation of two highly branched homogeneous polysaccharides, HC-PS1 and HC-PS3, with a molecular weight of 274 530 and 216 384 Da, respectively. The polysaccharides were purified by chromatography on DEAE-cellulose and Superdex columns. Their structural characterization was performed by IR, GC-MS, methylation, NMR, and SEM analysis. Both HC-PS1 and HC-PS3 are composed of eight types of monosaccharides, including rhamnose, arabinose, mannose, glucose, glucuronic acid, galactose, galacturonic acid, and xylose. The main linkages of the sugar residues in HC-PS1 include terminal Rhap, terminal and 1,5-linked Araf; 1,3,6-linked and 1,4,6-linked Manp; terminal, 1,4-linked, 1,3-linked, 1,3,6-linked and 1,4,6-linked and 1,3,4,6-linked Glcp; and terminal, 1,4-linked and 1,6-linked Galp. The main monosaccharide linkages in HC-PS3 are similar to that of HC-PS1, except the additional 1,3,4-linked Manp and the absence of 1,3,6-linked Glcp. HC-PS1 and HC-PS3 were found to inhibit complement activation through both the classical and alternative pathways with 50% inhibition concentrations of 0.272 – 0.318 mg/mL without interfering with the coagulation system. Preliminary mechanism studies indicated that both HC-PS1 and HC-PS3 inhibited the activation of the complement system by interacting with C2, C4, and C5. The results suggest that HC-PS1 and HC-PS3 could be valuable for the treatment of diseases associated with the excessive activation of the complement system.
Association between Salivary Fructosamine, Plasma Glycated Hemoglobin, and Plasma Glucose Levels among Type II Diabetes Mellitus and Nondiabetic Individuals—A Cross-sectional Study
Authors: Kandavel Sadhana , Kumar P.D Madan
Published: June 2019

Objective The study was aimed to determine the association between salivary fructosamine and plasma glycated hemoglobin, plasma fasting and postprandial glucose levels among patients suffering from type II diabetes mellitus and nondiabetic healthy individuals.

Materials and Methods The cross-sectional study was conducted in a hospital setting. A total of 100 participants were included, with 50 participants in each group—group I (patients with type II diabetes mellitus) and group II (nondiabetic healthy individuals). Blood and saliva samples were collected to estimate the levels of the blood and salivary parameters. Depending upon the normality, appropriate tests were used—t-test and Mann–Whitney U test were used for continuous data. Pearson chi-square test and Fisher's exact test were used for discrete data. To test for any positive association between salivary and blood parameters, simple linear regression was carried out.

Results The study results showed that group I had significantly higher levels of salivary fructosamine when compared to group II (p < 0.001). In groups I and II a significant positive association was observed between salivary fructosamine and plasma glycated hemoglobin (group I, r-value 0.893; group II, r-value 0.307).

Conclusion The overall study results showed that salivary fructosamine levels were significantly higher in patients with diabetes when compared to nondiabetic individuals. Also, positive correlation was observed between salivary fructosamine, plasma fasting, plasma postprandial, and plasma glycated hemoglobin among both the groups.
Traditional Medicine and Diabetes Care in Myanmar
Authors: Latt Tint Swe , Aye Than Than , U. Ei Sandar , Win Yin Yin , Wint Khin Thawdar , Khin Ei Thinzar
Published: June 2019

According to the National Survey of Diabetes and Its Risk Factors conducted in 2014, Myanmar has a high burden of diabetes, as the prevalence of diabetes in adult population was 10.5% and the estimated number of adults with diabetes was 2.5 million. Diabetes care in the country is still far from satisfaction, as more than 50% of people with diabetes were unaware of their diagnosis, and access to the comprehensive diabetes care is generally available in the big cities only. Moreover, most people have to pay the cost of health care out of their own pocket, as the health insurance system and social security system are currently in their rudimentary stage. Because of these gaps in diabetes care and health financing system, a significant number of people resort to the traditional medicine, which is familiar to a significant proportion of the public and also being relatively more accessible with affordable cost. This article assesses the current situation of traditional medicine in diabetes care in Myanmar and attempts to make some suggestions to remedy the drawbacks of traditional medicine. It discusses ways to adopt an integrated approach to strengthen the practice of traditional medicine, in general, in the health care system of the country regarding the diabetes care.
Is Anticoagulant Necessary in Patients with Coronary Artery Ectasia Presenting with Acute Coronary Syndrome? A Systematic Review of Case Reports
Authors: Pranata Raymond , Yonas Emir , Chintya Veresa , Alkatiri Amir Aziz
Published: June 2019

Coronary artery ectasia is found in 3 to 8% of patient's undergoing angiography and may sometimes induce acute myocardial infarction. Some articles reported a recurrence of acute coronary syndrome (ACS) in the presence of coronary artery ectasia (CAE). Our study aims to summarize the latest evidence on whether the use of anticoagulant in addition to SAPT/DAPT (single antiplatelet/dual antiplatelet) treating ACS with CAE patients is necessary. Since the trials concerning our objectives were scarce, we pooled case reports/series. We performed a comprehensive search on case reports/series on coronary artery ectasia that presented with acute coronary syndrome published until March 2019. We collected 13 cases from 11 reports. Out of 13 patients, 5 (38.5%) took DAPT only without anticoagulant and 8 (61.5%) took anticoagulant ± DAPT. Three out of five (60%) who took DAPT only, experienced recurrences at 1st and 2nd months' follow-up. The other two (40%) was uneventful at a mean of two months' follow-up. Eight patients who took anticoagulant were uneventful for a mean of 8.4 months. Those who took anticoagulant were at lower risk of experiencing ACS recurrence (p = 0.035). Two of the patients who experienced recurrence became 6 and 12 months free after optimal anticoagulation. The author of this study proposed that anticoagulant must be considered should SAPT/DAPT failed to provide adequate protection to the recurrence of ACS, especially in CAE patients who did not have other obvious stenotic lesions. However, the evidence is weak since this study only pooled case reports/series.
Correlation between lattice strain and physical (magnetic, dielectric, and magnetodielectric) properties of perovskite-spinel (Bi0.85La0.15FeO3)(1−x)–(NiFe2O4)(x) composites
Authors: Pandey Rabichandra , Pradhan Lagen Kumar , Kumar Sunil , Supriya Sweety , Singh Rakesh Kumar , Kar Manoranjan
Published: June 2019

Multiferroic composites are the current research interest due to their multi-functional behavior with promising electrical and magnetic properties compared to single crystallographic phase multiferroic materials. Hence, multiferroic composites of (1−x)Bi0.85La0.15FeO3-(x)NiFe2O4 (x = 0 to 0.50) have been investigated by considering Bi0.85La0.15FeO3 as a ferroelectric phase and NiFe2O4 as a magnetic phase. The crystal structure was examined by analyzing the X-ray diffraction (XRD) patterns. Different crystal structure parameters were obtained from the Rietveld refinement of XRD patterns. An increase in the lattice parameters of both Bi0.85La0.15FeO3 (BLFO) and NiFe2O4 (NFO) phases has been observed with the increase in the percentage of NiFe2O4 in the composites. Absorption peaks in Raman spectra shift toward lower frequencies with the increase in the percentage of NFO in the composite. Variation of lattice parameters and shifting of the Raman modes suggest the lattice strain at the interfaces of BLFO and NFO. Theoretical magnetizations were calculated for all composites by using the sum rule (using the magnetization of individual phases) and compared with experimentally observed magnetization. Interestingly, the experimental values of magnetizations of the composites are more than the theoretically calculated ones. It could be due to the lattice strain, which was observed from the XRD and Raman analysis.
Nanoscale n++-p junction formation in GeOI probed by tip-enhanced Raman spectroscopy and conductive atomic force microscopy
Authors: Prucnal Slawomir , Berencén Yonder , Wang Mao , Georgiev Yordan M. , Erbe Artur , Khan Muhammad B. , Boettger Roman , Hübner René , Schönherr Tommy , Kalbacova Jana , Vines Lasse , Facsko Stefan , Engler Martin , Zahn Dietrich R. T. , Knoch Joachim , Helm Manfred , Skorupa Wolfgang , Zhou Shengqiang
Published: June 2019

Ge-on-Si and Ge-on-insulator (GeOI) are the most promising materials for the next-generation nanoelectronics that can be fully integrated with silicon technology. To this day, the fabrication of Ge-based transistors with a n-type channel doping above 5 × 1019 cm−3 remains challenging. Here, we report on n-type doping of Ge beyond the equilibrium solubility limit (ne ≈ 6 × 1020 cm−3) together with a nanoscale technique to inspect the dopant distribution in n++-p junctions in GeOI. The n++ layer in Ge is realized by P+ ion implantation followed by millisecond-flashlamp annealing. The electron concentration is found to be three times higher than the equilibrium solid solubility limit of P in Ge determined at 800 °C. The millisecond-flashlamp annealing process is used for the electrical activation of the implanted P dopant and to fully suppress its diffusion. The study of the P activation and distribution in implanted GeOI relies on the combination of Raman spectroscopy, conductive atomic force microscopy, and secondary ion mass spectrometry. The linear dependence between the Fano asymmetry parameter q and the active carrier concentration makes Raman spectroscopy a powerful tool to study the electrical properties of semiconductors. We also demonstrate the high electrical activation efficiency together with the formation of ohmic contacts through Ni germanidation via a single-step flashlamp annealing process.