bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling stationary moving medium by static magneto-electric material
Authors: Gyimóthy Szabolcs
Published: January 2019

The electromagnetic equivalence of a stationary moving medium to magneto-electric materials is studied. The equivalent material characteristics of the medium at rest is obtained in terms of the diffusion tensor coefficient of the governing partial differential equation. Special attention is paid to the transition condition of field quantities on the boundary of the moving medium; it is found that the nonmoving magneto-electric equivalent model must be supplied with surface sources. The method is demonstrated through examples and verified by finite element simulation.
Estimating Al2O3–CO2 nanofluid viscosity: a molecular dynamics approach
Authors: Ahmed Zeeshan , Bhargav Atul , Mallajosyula Sairam S.
Published: January 2019

High-viscosity CO2 is of interest to the oil and gas industry in enhanced oil recovery and well-fracturing applications. Dispersing nanoparticles in CO2 is one way of achieving increased viscosity. However, parametric studies on viscosity estimation of CO2 nanofluids is not found in the open literature. A comparison of various interatomic potentials for their accuracy in predicting viscosity is also missing. In this work, we studied Al2O3 nanoparticles in CO2 base fluid. We screened the inter-molecular interaction potential models available for CO2–CO2 interactions and found that the TraPPE-flexible model (with MORSE potential) to be most suitable for conditions used in this work. We estimated the CO2–Al2O3 interaction potential using quantum mechanical simulations. Using this combination for CO2–CO2 and CO2–Al2O3 interactions, we explored the effects of temperature and nanoparticle size on viscosity using molecular dynamics simulations (MD). We predicted that the viscosity would increase with increase in temperature and particle size. We also calculated the base fluid self-diffusion coefficient to investigate the effect of Brownian motion and its contribution to changes in viscosity. We found that it decreases with increase in particle size and temperature, thereby indicating that Brownian motion does not contribute to the increased viscosity. Further, the nanolayer formed at the Al2O3–CO2 interface is studied through density distributions around the nanoparticle; the thickness of this nanolayer is found to increase with nanoparticle diameter. Finally, we examined the structures of CO2 fluid in presence of nanoparticles at different thermodynamic states through radial distribution functions. The current work sheds light on the viscosity enhancement by the addition of nanoparticles; it is hoped that such studies will lead to tools that help tailor fluid properties to specific requirements.
Effects of pulsed electrodeposition parameters on the properties of zinc oxide thin films to improve the photoelectrochemical and photoelectrodegradation efficiency
Authors: Lakhdari Meriem , Habelhames Farid , Nessark Belkacem , Girtan Mihaela , Derbal-Habak Hassina , Bonnassieux Yvan , Tondelier Denis , Nunzi Jean Michel
Published: January 2019

Zinc oxide (ZnO) thin films were synthesized on ITO glass substrates by electrochemical deposition from a nitrate solution. The deposition potential, bath temperature and annealing temperature were fixed at −1.1 V versus SCE, 80 and 400 °C, respectively. Firstly, we prepared the ZnO thin films by two different electrochemical methods: direct (DE) and pulsed electrodeposition (PE). The results indicate that pulse electrodeposition improves the properties of ZnO thin films compared to direct electrodeposition technique. Secondly, we chose the PE method for the elaboration of ZnO thin films and we varied the time-On (ton) from 7 to 1 s. Deposited ZnO thin films were characterized using XRD, SEM, optical and photocurrent measurement. X-ray diffraction results indicate that the synthesized ZnO has a pure hexagonal wurtzite structure with a marked preferential orientation along the (002) plane perpendicular to the substrate. SEM analysis reveals that the electrodeposited nanosheets at time-On of 7 s are only hexagonal. A remarkable change in ZnO morphology from nanosheets to nanosheets/nanorods and decrease in gap energy is observed with the decrease in electrodeposition time-On. After optimization in electrodeposition time (ton), a significant improvement in photocurrent and Methylene Blue (MB) photoelectrocatalytical degradation were observed.
The dynamics of nucleate boiling of salt solutions at a high heat flux
Authors: Morozov Vladimir , Elistratov Dmitriy
Published: January 2019

In this paper, experimental results are obtained for the desorption of layers of aqueous salt solutions of LiBr and CaCl2at a temperature of nucleate boiling on a horizontal heating surface. The wall temperature is 130 °C. The required volume of the solution with a given mass concentration is placed on the working surface using the Thermo Scientific dispensers. After that, the desorption rate continuously decreases over time. A decrease in the wall temperature leads to a drop in the intensity of the bubbling boiling. The effect of gas convection during evaporation and thermal radiation is small in comparison with the heat of evaporation.
Two-phase cooling system with controlled pulsations
Authors: Eloyan Karapet , Kreta Alexey , Tkachenko Egor
Published: January 2019

One of the promising ways of removing large heat fluxes from the surface of heat-stressed elements of electronic devices is the use of evaporating thin layer of liquid film, moving under the action of the gas flow in a flat channel. In this work, a prototype of evaporative cooling system for high heat flux removal with forced circulation of liquid and gas coolants with controlled pulsation, capable to remove heat flux of up to 1,5 kW/cm2 and higher was presented. For the first time the regime with controlled pulsation is used. Due to pulsations, it is possible to achieve high values of critical heat flux due to a brief increase in the flow rate of the liquid, which allows to "wash off" large dry spots and prevent the occurrence of zones of flow and drying.
Critical heat flux in a closed two-phase thermosyphon
Authors: Ponomarev Konstantin , Islamova Anastasiya , Dmitry Feoktistov
Published: January 2019

A closed two-phase thermosyphon experimental setup with the possibility of recording the coolant and its vapors temperatures was developed. We proved the use of the V. M. Borishansky and S. S. Kutateladze correlations for the determination of the critical heat flux in closed two-phase thermosyphons with the ratio of their internal diameter to
the length of the heat supply zone in the range of 1 < dBhym / Lu < 2.
Two–phase flow of air–water mixture in a minichannel
Authors: Ronshin Fedor , Eloyan Karapet , Cheverda Viacheslav
Published: January 2019

Two-phase systems have a huge potential for solving problems of removing large heat fluxes. To date, mini-channel and microchannel systems are widespread. Of particular interest are the stratified flow regime and the annular flow regime in mini- and micro- channel. It is necessary to know in detail the map of flow regimes for the realization of these flow
regimes. In this paper, we present an investigation of flow regimes for a rectangular mini- channel 10 mm wide and 1.1 mm high.
Water pulsating heat pipe
Authors: Cheverda Viacheslav , Ronshin Fedor
Published: January 2019

The new experimental setup with copper-glass pulsating heat pipe has been constructed for investigation of the heat transfer problem. Pulsations of liquid slugs inside the heat pipe has been observed. It is demonstrated that with increasing of temperature difference between evaporator and condenser heat flux which can be removed is also increases.
Heat transfer during drop impact on a heated foil
Authors: Ponomarenko Tatiana , Safonov Aleksey
Published: January 2019

The heat transfer during impact, evaporation and dynamics of the water drop on the heated thin constantan foil have been studied. The function of diameter versus time is constructed.
Characteristics of Boiling Heat Transfer on Hydrophobic Surface
Authors: Surtaev Anton , Serdyukov Vladimir , Safonov Alexey
Published: January 2019

The paper presents the results of an experimental study of the effect of hydrophobic fluoropolymer coating on the multiscale characteristics of heat transfer at water boiling. New experimental data on dynamics of vapor bubble growth and detachment, evolution of contact line, nucleation site density, heat transfer coefficient were obtained using high-speed imaging techniques, including infrared thermography and video recording from the bottom side of transparent ITO heater. It was shown, that the using of hydrophobic fluoropolymer coating leads to heat transfer enhancement, to decrease of the superheat temperature at the onset of boiling, to increase of the active nucleation site density and to significant change in the dynamics of growth and departure of vapor bubbles and the evolution of the triple contact line.
Assessment of the impact of vibrations on the track surface from impact loads
Authors: Jukowski Michał , Śledziewski Krzysztof , Hypki Mateusz
Published: January 2019

Dynamic development of the linear infrastructure in Poland directly contributed to the increase in the number of engineering sites and facilities. Due to ground conditions and values of exploitation loads, in some cases bridge supports must be placed on foundation piles, the method of execution of which may cause significant dynamic impact on the structures located in the close vicinity. The paper assesses the impact of dynamic actions resulting from impact loads during impact pile driving of FRANKA piles with the use of a guide pipe on the railway track surface, on which there is continuous railway vehicle traffic. The tests have shown that the serviceability limit condition has been met and that the construction works do not result in exceeded values of vibration acceleration.
Indoor vehicle tracking with a smart MEMS sensor
Authors: Cechowicz Radosław , Bogucki Marcin
Published: January 2019

Indoor navigation and vehicle tracking require special measurement techniques. The reference points and routes used by classic AGV (Automated Guided Vehicle) systems are usually buried under floor surface or painted directly on the floor, thus limiting the set of possible transportation paths. However, the indoor environment of an industrial warehouse is dynamic, the number and location of objects inside are subject to frequent changes and these changes might not be reflected in the map of the area. In such conditions, navigation according to the on-board instruments (dead-reckoning) could provide valuable information about the position and orientation of the vehicle. This paper reports test results from a smart sensor using a 6-axis MEMS IMU unit and a self-calibrating procedure for indoor vehicle orientation tracking. The smart sensor, integrated with information from wheel encoders can produce 2D position coordinates suitable for navigation. Original data processing algorithm, applied in the sensor, was developed by the authors as a part of the research project on mobile robotics.
Collective decision making in dynamic vehicle routing problem
Authors: Kucharska Edyta , Grobler-Dębska Katarzyna , Klimek Radosław
Published: January 2019

The paper presents a collective decision making in dynamic vehicle routing problem. In contrast to the static problem, a part or all of the customers’ companies are revealed dynamically during the design or execution of the routes. The problem is modelled using the algebraic-logical meta-model (ALMM) methodology, which enables making collective decisions in successive process stages, not separately for individual vehicles. ALMM is considered to be the rule according to which the availability of companies is determined. The steps and schematics of the general algorithm that take into account the dynamic appearance of new companies are shown. The proposed approach belongs to trajectory-based metaheuristics methods.
Effect of Cylindrical Turbulators on the Mixing Process in Basic Venturi Gas Mixer Using OpenFOAM
Authors: Romańczyk Mathias , Elsner Witold
Published: January 2019

This study was devoted to improving the mixing quality in a Venturi gas mixer. It is well known that the performance of industrial gas engines strongly depends on the quality of air and fuel mixture and therefore on its homogeneity. Incorrect mixture proportions may lead to unstable operation of the entire industrial gas engine and excessive emissions exceeding environmental standards of the European Union. The effectiveness of the mixing process in a Venturi gas mixer depends on many factors, i.e. correct proportions between Air inlet, Venturi Throat diameter, as well as gas inlet area. To improve the intensification of the whole mixing process, as well as to increase the mixing time between gas and air, it was decided to insert disturbing elements in form of cylindrical turbulators into the Venturi pipe. Therefore numerical calculations were performed for the most commonly consumed by industrial gas engines lean Air-Fuel mixture, with an air excess coefficient ratio of λ = 1.6. In numerical analysis, OpenFOAM software was used to investigate the impact of cylindrical turbulators on the whole mixing process in a basic Venturi gas mixer. Particular attention was focused on the Air-Fuel Ratio (AFR) changes, Turbulent Kinetic Energy (TKE) and Pressure loss [Pa], which is one of the most qualitative evaluation parameters of a gas mixer.
FEM simulation of water lost through damaged household water connection
Authors: Iwanek Małgorzata , Suchorab Paweł , Suchorab Zbigniew
Published: January 2019

The problem of water supply pipe’s failures is one of the most onerous for water distribution network’s (WDN) operators. Multiple actions undertaken to detect, minimise and eliminate the phenomenon of water losses are mainly focused on financial aspect of lost water. However, at some point, the further minimisation of water losses is unprofitable due to reaching the economic level of water leakages. In WDNs failures analysis the biggest emphasis is put on damages of main pipes and distribution pipes, while failures of household water connections are often neglected. That is because the most typical water losses in household connections are hard-to-detect background leakages with relatively small water outflow. Still, in a long-time perspective, such leakages can cause significant water losses. The aim of this paper was to evaluate the parameters of water lost through damaged household water connection (volume, velocity, suffosion conditions). The basis for the analysis were laboratory investigations and a numerical simulation of a pipe failure using the FEFLOW v. 5.3 software. The results of the simulation, compared with laboratory tests results, enabled to state that, contrary to the widespread practice, leakages from household connections cannot be ignored.
The simulation study on the multipath adaptive video transmission
Authors: Przylucki Slawomir , Czerwinski Dariusz
Published: January 2019

The article presents simulation studies of multipath video transmission implemented as a live monitoring system based on adaptive streaming mechanisms. The transmission network consists of the Wi-Fi infrastructure and a single LTE cell. Both wireless networks are used during the operation of the video monitoring system. The analysis of the obtained results allows us to compare the features of two currently used multipath transmission protocols, MultiPath Quick UDP Internet Connections (MPQUIC) and MultiPath TCP (MPTCP) in the context of their use in adaptive video streaming systems. Also, the article contains a summary of the perceived advantages and disadvantages of using several transmission networks simultaneously for the implementation of video surveillance and monitoring systems.
Application of sewage sludge for the production of construction
Authors: Czechowska-Kosacka Aneta
Published: January 2019

The paper presents the studies pertaining to sewage sludges and their mixtures with fly ash to be used as an additive for the manufacturing of construction materials. The studies were carried out using X-ray diffraction. The form and morphology of samples as well as the chemical composition in the micro-area were determined using a scanning electron microscope. The obtained results indicate the possibility of using sewage sludges for construction purposes. In the produced mixtures, an increase in the content of anhydrite and rock-forming calcite was noted in relation to the sludge. Production of the construction materials should be preceded with additional strength tests of the obtained product in order to determined the percentage of waste material addition.
Concept and modelling of the electrohydraulic valve with DC and stepper motors
Authors: Rybarczyk Dominik
Published: January 2019

The article describes concept and modelling of a new type of electrohydraulic valve controlled by the combination of a stepper motor and a DC motor. The aim of this invention is to use in the proportional valve two motors with the different properties. Both motors are responsible for the movement of a valve spool. The stepper motor and the DC motor are connected to a shaft by using a bellows coupling. Transfer from rotary to linear motion is performed by use of a bolt-nut system. According to the invention, presented here valve can be used in hydraulic drive systems with high positioning accuracy requirement. The author was granted a patent no. P.421994 on the invention described in this paper.
Controlling the industrial robot model with the hybrid BCI based on EOG and eye tracking
Authors: Kubacki Arkadiusz , Jakubowski Arkadiusz
Published: January 2019

The article describes the design process of building a hybrid brain-computer interface based on Electrooculography (EOG) and centre eye tracking. In the first paragraph authors presented theoretical information about Electroencephalography (EEG), Electrooculography (EOG), and Eye. Authors prepared an overview of the literature concerning hybrid BCIs. The interface was built with use of bioactive sensors mounted on the head. Movement of industrial robot model was triggered by a signal from eyes movement by EOG and eye tracking. The built interface has been tested. Three experiments were carried out. In all experiments, three people aged 25-35 were involved. 30 attempts per scenario were recorded. Between each attempt, a respondent had a 1-minute break. The investigators attempted to move cube from one table to the other.
Data-driven monitoring of the gearbox using multifractal analysis and machine learning methods
Authors: Puchalski Andrzej , Komorska Iwona
Published: January 2019

Data-driven diagnostic methods allow to obtain a statistical model of time series and to identify deviations of recorded data from the pattern of the monitored system. Statistical analysis of time series of mechanical vibrations creates a new quality in the monitoring of rotating machines. Most real vibration signals exhibit nonlinear properties well described by scaling exponents. Multifractal analysis, which relies mainly on assessing local singularity exponents, has become a popular tool for statistical analysis of empirical data. There are many methods to study time series in terms of their fractality. Comparing computational complexity, a wavelet leaders algorithm was chosen. Using Wavelet Leaders Multifractal Formalism, multifractal parameters were estimated, taking them as diagnostic features in the pattern recognition procedure, using machine learning methods. The classification was performed using neural network, k-nearest neighbours’ algorithm and support vector machine. The article presents the results of vibration acceleration tests in a demonstration transmission system that allows simulations of assembly errors and teeth wear.
Portfolio approach to project management in creation of the organization’s value
Authors: Kaczorowska Anna , Słoniec Jolanta , Motyka Sabina
Published: January 2019

The composition and structure of the project portfolio were analysed and the importance of the links between particular projects and with the organization’s strategy in creating of its value were emphasised in the article. As regards the information projects, profoundly analysed were the subprocesses of identification, categorization, evaluation of components, and balancing of the whole portfolio, besides the tools were proposed for them which involve the specificity of ICT undertakings, optimise the use of the organisation’s resources and enable economically justified choice of projects for the portfolio. The applied research methods comprise a cross-sectional analysis of literature and analytical method. In result of the presented considerations a growing role of the portfolio approach to project management was shown along with its importance in creation of the contemporary organization’s values, and the need to continue the research in the selected area was demonstrated.
The influence of the nucleus pulposus on the stress distribution in the natural and prosthetic intervertebral disc
Authors: Karpiński Robert , Jaworski Łukasz , Jonak Józef , Krakowski Przemysław
Published: January 2019

The aim of this article was to present the results of a preliminary study on the stress distribution in the lumbar intervertebral disc [IVD] under loads induced during daily activities. Basic anatomy, biomechanical analysis of the vertebra and intervertebral disc were introduced. The third and fourth lumbar vertebrae were chosen for the study because they carry considerably higher loads, especially while standing or sitting. The static mechanical analyses using the finite element method (FEM) were conducted for four standard loads reflecting patient’s positions: recumbent, standing, sitting and standing with additional loads, and three models: an intervertebral disc with an inner nucleus pulposus and two prosthetic intervertebral discs, with or without an artificial nucleus. The FEM analysis was performed in the SolidWorks Simulation module on reverse-engineered 3D models of vertebrae and the intervertebral disc, based on a series of computed tomography [CT] scans of the patient’s spine, which had been properly processed in Materialise Mimics software and exported to CAD files. The model of the fourth intervertebral disc, placed between third and fourth vertebra, had been additionally modified to include its inner core, the nucleus pulposus.
Stress distribution in the knee joint in relation to tibiofemoral angle using the finite element method
Authors: Karpiński Robert , Jaworski Łukasz , Jonak Józef , Krakowski Przemysław
Published: January 2019

The article presents the results of a preliminary study on the structural analysis of the knee joint, considering changes in the mechanical properties of the articular cartilage of the joint. Studies have been made due to the need to determine the tension distribution occurring in the cartilage of the human knee. This distribution could be the starting point for designing custom made human knee prosthesis. Basic anatomy, biomechanical analysis of the knee joint and articular cartilage was introduced. Based on a series of computed tomography [CT] scans, the 3D model of human knee joint was reverse-engineered, processed and exported to CAD software. The static mechanical analysis of the knee joint model was conducted using the finite element method [FEM], in three different values of tibiofemoral angle and with varying mechanical properties of the cartilage tissue. Main conclusions of the study are: the capability to absorb loads by articular cartilage of the knee joint is preliminary determined as decreasing with increasing degenerations of the cartilage and with age of a patient. Without further information on changes of cartilage’s mechanical parameters in time it is hard to determine the nature of relation between mentioned capability and these parameters.
Numerical analysis of crack propagation in a pull-out test
Authors: Gontarz Jakub , Podgórski Jerzy
Published: January 2019

This paper describes the computer analysis of the pull-out test for determining the force needed to pull out a rock fragment, and the shape of this fractured fragment. The material analysed is sandstone. The analysis included a comparison of the various crack propagation methods in computer program using the Finite Element Method. The work also contains a description of performed laboratory tests and analytical considerations.
Modification of tribological tester t-01m allowing testing in conditions of lubrication
Authors: Sadowski Piotr , Czajka Emil
Published: January 2019

Researchers often want to develop their experiments in terms of wide range of testing conditions and results possible to acquire. One way to achieve this is to adapt existing testing equipment to new requirements. This paper proposes a method for extending the capabilities of the T-01M tester with a pressure lubrication system of a pin on disc contact, its construction and adjustments. Tribological tests carried out with the presence of a lubricant showed the correct functioning of the modified tester. We obtained several variables for the selected friction pair and friction parameters in the lubricated joint: friction force, friction coefficient, mass wear, friction work, wear intensity and specific wear. Verification tests confirmed suitability of the tester modification, adapting it to friction and wear tests in a lubricated contact. The expanded stand can be used (in the future) for tribological tests of lubricated frictional pairs to measure friction, wear, friction pairs temperature and to compare used lubricants.
The analysis of influence of polymer admixtures on properties of lightweight concrete
Authors: Góra Jacek , Barnat-Hunek Danuta , Wlaź Paweł , Garbacz Monika
Published: January 2019

The article presents the results of testing physical and strength properties of concrete with the addition of lightweight perlite in the amount of 10 and 20%. The additive was introduced by volume substituting a part of the sand. In addition, the effect of using siloxane admixtures and a vinyl acetate copolymer with different degree of dosing, as well as applied simultaneously, were analysed. The tests were carried out in the field of bulk density and proper density, determination of tightness and porosity, compressive strength and tensile strength after 28 days of maturation. In terms of durability of concrete, absorption and resistance of concretes to the freeze-up effects after 100 freezing and thawing cycles were tested. The results of the study were subjected to statistical analysis using the analysis of variance. The analysed factors of influence were the amount of perlite addition, as well as the type and amount of the added admixture
Computer measurement of the friction of thin metal structure created in PVD technology on the flexible substrate
Authors: Korzeniewska Ewa , Szczęsny Artur , Józwik Jerzy , Tofil Arkadiusz
Published: January 2019

The paper presents the results of research study on the phenomenon of friction of thin film electroconductive structure created on composite flexible substrate and results of measurement of the friction coefficient. Tribological tests were performed on T-01M tribotester. The measurement tests were conducted according to ASTM G133 standard with a minimum force of 1N. A ball-on-disc friction combination was used. The study was conducted at a fixed temperature of 28 ° C. Due to the nature of the tested samples, non-standard test parameters were used: test time 100 s, data acquisition frequency 10 Hz, slip velocity of the friction node 0.3 m/s on a radius of 11 mm. Based on the obtained results, the friction coefficient of the thin metallic layer Ag and Cu was determined. The obtained mean friction coefficient for a silver layer was 0.59, while for a thin copper layer 0.67. The knowledge of the determined coefficients will allow for effective and optimal use of the textronics materials tested in practical applications. The research methodology does not support determining the usage of the ball-on-disc pair.
Statistical methods in the context of environmental quality assessment: On the example of riparian beetles (Coleoptera, Carabidae)
Authors: Kirichenko-Babko Marina , Danko Yaroslav , Guz Łukasz , Majerek Dariusz , Babko Roman
Published: January 2019

Modern environmental research involves the use of a broad range of statistical methods and programs. In any study, the results are obtained, as a rule, using statistical calculations, beginning with the calculation of reliability of data, and ending with complex statistical methods that allow estimating trends and predicting the processes that are evaluated. However, there is a problem associated with the correct interpretation of biological results by experts in statistics and, accordingly, the correctness of the choice and application of various statistical methods by biologists. In this paper, the evaluation of the results of studies of the effect of changes in the hydrological regime of the river caused by the functioning of the dam on the structure and spatial distribution of riparian carabids was considered. On the banks of intact rivers, the structure of the riparian assemblage naturally changes depending on the quality of coastal sediments. In order to assess the changes in the structure of the riparian assemblage, a number of statistical methods were employed. It was shown that not every method will adequately interpret the results of ecological studies. The differences in obtaining adequate interpretations while using various statistical methods were understood.
Study of Strain-Softening Stage in Structurally Inhomogeneous Materials
Authors: Mironov Vladimir , Lukashuk Olga
Published: January 2019

The paper considers – in terms of modeling and experimental testing – the softening stage manifested in structurally inhomogeneous materials under quasi-static and cyclic load. The method which is used to build the theoretical basis is typical for mechanics. It starts with defining a new material property – strain-softening phase. The stage is realized in the form of a descending branch of the curve on computer diagrams recorded during simple tension or torsion tests on non-reusable specimens in a reasonably rigid testing machine. The type of such a diagram is determined by the structural inhomogeneity of a material, which is defined by distribution law for strength and plasticity properties of structural elements. Complete stress-strain curves or diagrams (CSSD) with a branch descending to zero have been plotted for materials of various classes. Degradation of parameters of a descending branch on a computer diagram recorded for trained specimens provides a new angle on the subject of relation between static and cyclic material properties. The experiments and modeling which were carried out provide basic understanding of softening in terms of deformation.
The Relationships of Self-regulated Learning and Academic Achievement in University Students
Authors: Xiao Sanrong , Yao Kang , Wang Ting
Published: January 2019

Self-regulated learning plays an important role in academic achievement. This paper introduces
the relationship between self-regulated learning and academic achievement. Many connections between
self-regulated learning and academic achievement have been suggested, such as purposive and goal
oriented,incorporating and applying a variety of strategic behaviors. Also it provides some evidences in the
mediating effect of academic achievement on the relationship between self-regulated learning and academic
achievement. At the end, it questions the existing conclusions and puts forward some researches on main
directions where future research should be focused, and the enhancement of previous study.
Psychosocial Predictors of Acculturative Stress among Female and Male Immigrant Asian Americans: A Gender Comparison Study
Authors: Xiao Sanrong , Liu Ranran , Yao Kang , Wang Ting
Published: January 2019

The purpose of this study was to examine whether gender differences existed and how the predictors were linked to acculturative stress across gender among a national sample of 1639 immigrant Chinese, Filipino, Vietnamese, and other Asian Americans. The data were from the National Latino and Asian American Study (NLAAS) conducted in 2002 and 2003, the first national epidemiological household survey of Asian Americans in the United States. The participants took part in face-to-face interviews, which were conducted with computer-assisted interviewing software in Mandarin, Cantonese, Tagalog, Vietnamese, and English. After fitted bivariate correlations to examine the relationships between acculturative stress and psychosocial variables, data were analyzed using two multiple regressions to identify the most significant predictors of acculturative stress for men and women separately. Results indicated that the psychosocial predictors of acculturative stress varied with gender status. For all men and women, longer years in the U.S., higher English proficiency, and less perceived discrimination predicted related to less acculturative stress. Social network was not the predictor for both men and women. Age of immigration, marital status, family cohesion and social position were additional significant predictors of acculturative stress only for men, but not for women. The implications of these results were discussed.
Study on the strategy of improving self-learning ability of College Students
Authors: Ziyu Liu , Jing Xiao
Published: January 2019

College students are the main force of social development and construction in China, and at present, autonomous learning is an important topic in higher education research. Therefore, mastering autonomous learning ability is very important for contemporary college students. This paper discusses the reasons that affect college students' self-learning from the aspects of schools, teachers, students and society, and gives the strategies and measures to enhance the self-learning ability of college students according to reasons. It provides useful reference for quality colleges and universities to cultivate students.
Estimating the solar wind pressure at comet 67P from Rosetta magnetic field measurements
Authors: Timar Aniko , Nemeth Zoltan , Szego Karoly , Dósa Melinda , Opitz Andrea , Madanian Hadi
Published: January 2019

Aims: The solar wind pressure is an important parameter of space weather, which plays a crucial role in the interaction of the solar wind with the planetary plasma environment. Here we investigate the possibility of determining a solar wind pressure proxy from Rosetta magnetic field data, measured deep inside the induced magnetosphere of comet 67P/Churyumov-Gerasimenko. This pressure proxy would be useful not only for other Rosetta related studies but could also serve as a new, independent input database for space weather propagation to other locations in the Solar System.

Method: For the induced magnetospheres of comets the magnetic pressure in the innermost part of the pile-up region is balanced by the solar wind dynamic pressure. Recent investigations of Rosetta data have revealed that the maximum magnetic field in the pile-up region can be approximated by magnetic field measurements performed in the inner regions of the cometary magnetosphere, close to the boundary of the diamagnetic cavity, from which the external solar wind pressure can be estimated.

Results: We were able to determine a solar wind pressure proxy for the time interval when the Rosetta spacecraft was located near the diamagnetic cavity boundary, between late April 2015 and January 2016. We then compared our Rosetta pressure proxy to solar wind pressure extrapolated to comet 67P from near-Earth. After the exclusion of disturbances caused by transient events, we found a strong correlation between the two datasets.
A consistent bridge for the construction of generalized nonclassical states for confined systems through the inclusion of inverse generators in the algebraic formalism
Authors: Aleixo A. N. F. , Balantekin A. B.
Published: January 2019

We consider quantum confined systems represented by supersymmetric quantum mechanics where the Hamiltonians are products of two operators. We introduce inverses of these operators as well as pair operators, which are products of the original operators and their inverses. We show that the eigenstates of these pair operators are purely squeezed states, and using them we construct raised and decreased extensions of the squeezed states. We apply this procedure both to the ladder-operator and to the displacement-operator methods, showing the equivalence between those the two approaches. Finally, we show how the raised and decreased squeezed states can be dynamically produced by coupling the Hamiltonian with a two-level atom.
Solving Fresnel equation for refractive index using reflected optical power obtained from Bessel beam interferometry
Authors: Gupta Pooja , Pandey Amit , Vairagi Kaushal , Mondal Samir K.
Published: January 2019

This work demonstrates an interferometric technique to estimate the reflected powers from dielectric interfaces and the reflection coefficient using the Fresnel equation for measurement of the refractive index (RI) of liquid samples. It uses low-coherence common-path optical interferometry that is commonly used for optical imaging. A uniquely designed optical fiber tip generating a high-quality non-diffractive Bessel beam probes liquid samples in a glass container non-invasively. The light reflected from different interfaces of the container is recollected by the same optical fiber tip. The reflected beams interfere with the reference beam generated at the fiber tip itself. This interference spectrum is further processed using fast-Fourier transform to measure reflected powers from the respective interfaces. The acquired powers are used to solve the Fresnel equation to find RI of liquid samples. As a proof of concept, experiments have been performed on several liquid samples including turbid media such as blood. This non-invasive interferometric technique could also be an ideal example confirming the Fresnel equation for reflection of light. Unlike other optical fiber-based RI sensors, this technique does not require temperature compensation. The method can be employed for inspection of the production process in terms of RI in pharmaceutical and chemical process plants, etc.
Structural and electrical characterization of NaNbO3-PVDF nanocomposites fabricated using cold sintering synthesis route
Authors: Gyan Deepankar Sri , Dwivedi Akansha
Published: January 2019

Sodium niobate (NaNbO3) powders and nanowires were synthesized and subsequently used for preparing composites with polyvinylidene-fluoride (PVDF) using the cold sintering technique in the weight ratio of 80:20 (ceramic:polymer). Phase purity of ceramic powders and nanowires was confirmed by X-ray diffraction analysis. Different phases of PVDF formed under various process parameters were also identified. Thermo-gravimetric analysis was performed in order to check the thermal stability of the composites. SEM was used to study the surface morphology of these samples, and energy dispersive x-ray analysis was also carried out in order to view the distribution of polymers in the composites. Furthermore, the formation of the ceramic matrix in the composites was verified and distribution of polymers in the ceramic matrix was examined by micro-computed tomographic analysis. Dielectric constant and loss tangent were measured and compared with the theoretically calculated values. Theoretical breakdown strength and energy density were calculated and were found to be as high as 1345 kV/cm and 6.1 J/cm3, respectively, at room temperature. Discharge efficiency of 64% was obtained for annealed nanocomposites.
Valley-projected edge modes observed in underwater sonic crystals
Authors: Shen Yuanyuan , Qiu Chunyin , Cai Xiangxi , Ye Liping , Lu Jiuyang , Ke Manzhu , Liu Zhengyou
Published: January 2019

Here, we report an experimental study on the valley-projected edge states for underwater sound, which propagates along the interface separating two topologically distinct acoustic valley Hall insulators. The topological edge states are directly observed in our ultrasound scanning experiments, together with a solid evidence for the valley-selective excitation. Furthermore, we demonstrate an intriguing sound splitter built by topologically different acoustic valley Hall insulators. All experimental data agree well with our numerical results. Prospective applications can be anticipated, such as for underwater sound signal processing and ocean noise control.
Anticipation via canards in excitable systems
Authors: Köksal Ersöz Elif , Desroches Mathieu , Mirasso Claudio R. , Rodrigues Serafim
Published: January 2019

Neurons can anticipate incoming signals by exploiting a physiological mechanism that is not well understood. This article offers a novel explanation on how a receiver neuron can predict the sender’s dynamics in a unidirectionally-coupled configuration, in which both sender and receiver follow the evolution of a multi-scale excitable system. We present a novel theoretical viewpoint based on a mathematical object, called canard, to explain anticipation in excitable systems. We provide a numerical approach, which allows to determine the transient effects of canards. To demonstrate the general validity of canard-mediated anticipation in the context of excitable systems, we illustrate our framework in two examples, a multi-scale radio-wave circuit (the van der Pol model) that inspired a caricature neuronal model (the FitzHugh-Nagumo model) and a biophysical neuronal model (a 2-dimensional reduction of the Hodgkin-Huxley model), where canards act as messengers to the senders’ prediction. We also propose an experimental paradigm that would enable experimental neuroscientists to validate our predictions. We conclude with an outlook to possible fascinating research avenues to further unfold the mechanisms underpinning anticipation. We envisage that our approach can be employed by a wider class of excitable systems with appropriate theoretical extensions.
Slow- and rapid-scan frequency-swept electrically detected magnetic resonance of MOSFETs with a non-resonant microwave probe within a semiconductor wafer-probing station
Authors: McCrory Duane J. , Anders Mark A. , Ryan Jason T. , Shrestha Pragya R. , Cheung Kin P. , Lenahan Patrick M. , Campbell Jason P.
Published: January 2019

We report on a novel electron paramagnetic resonance (EPR) technique that merges electrically detected magnetic resonance (EDMR) with a conventional semiconductor wafer probing station. This union, which we refer to as wafer-level EDMR (WL-EDMR), allows EDMR measurements to be performed on an unaltered, fully processed semiconductor wafer. Our measurements replace the conventional EPR microwave cavity or resonator with a very small non-resonant near-field microwave probe. Bipolar amplification effect, spin dependent charge pumping, and spatially resolved EDMR are demonstrated on various planar 4H-silicon carbide metal-oxide-semiconductor field-effect transistor (4H-SiC MOSFET) structures. 4H-SiC is a wide bandgap semiconductor and the leading polytype for high-temperature and high-power MOSFET applications. These measurements are made via both “rapid scan” frequency-swept EDMR and “slow scan” frequency swept EDMR. The elimination of the resonance cavity and incorporation with a wafer probing station greatly simplifies the EDMR detection scheme and offers promise for widespread EDMR adoption in semiconductor reliability laboratories.
Turbulent electromagnetic fields at sub-proton scales: Two-fluid and full-kinetic plasma simulations
Authors: González C. A. , Parashar T. N. , Gomez D. , Matthaeus W. H. , Dmitruk P.
Published: January 2019

Plasma dynamics is a multi-scale problem that involves many spatial and temporal scales. Turbulence connects the disparate scales in this system through a cascade that is established by nonlinear interactions. Most astrophysical plasma systems are weakly collisional, making a fully kinetic Vlasov description of the system essential. The use of reduced models to study such systems is computationally desirable, but careful benchmarking of physics in different models is needed. We perform one such comparison here between the fully kinetic Particle-In-Cell model and a two-fluid model that includes Hall physics and electron inertia, with a particular focus on the sub-proton scale electric field. We show that in general, the two fluid model captures large scale dynamics reasonably well. At smaller scales, the Hall physics is also captured reasonably well by the fluid code, but electron features show departures from the fully kinetic model. Implications for the use of such fluid models are discussed.
Understanding the mechanism of hardness enhancement in tantalum-substituted tungsten monoboride solid solutions
Authors: Lei Jialin , Yeung Michael T. , Mohammadi Reza , Turner Christopher L. , Yan Jinyuan , Kaner Richard B. , Tolbert Sarah H.
Published: January 2019

The differential strain behavior of TaxW1-xB solid solutions has been studied as a function of composition using high-pressure radial X-ray diffraction in a diamond-anvil cell under non-hydrostatic pressure (up to ∼65 GPa) to understand the hardening mechanisms in this family of materials. The hardness of tungsten monoboride (WB) can be increased by adding tantalum and reaches a maximum at a doping level of 50 at. % with a value of 42.8 ± 2.6 GPa under an applied load of 0.49 N. Plateaus were observed in the differential strain data for both the (020) and (002) directions, suggesting that this is the primary slip system in this material. These plateaus were modified by the addition of Ta, indicating that strengthening of the (002) and (020) planes by solid solution hardening was primarily responsible for the hardness enhancements in TaxW1-xB solid solutions. In contrast, the differential strain supported by the (200) plane linearly increases with pressure up to the highest pressures reached in this work (>60 GPa) and shows almost no change with metal composition. Because of the very different compression behavior in the (200) and (020) planes, change in the b/a ratio with pressure provides a unique way to visualize the onset of plastic behavior. This onset varies from ∼15 GPa for samples with 5% Ta to more than 30 GPa for the sample with 50% Ta. In addition, the ambient bulk modulus of each solid-solution sample was determined using the second-order Birch-Murnaghan equation-of-state and found to be ∼340 GPa for all phases.