scholarly journals Research of resonance vibrations of the system «Telescopic screw — bulk medium» caused by torsional vibrations

2020 ◽  
Vol 98 (2) ◽  
pp. 119-126
Author(s):  
V. Hud ◽  
◽  
I. Hevko ◽  
O. Lyashuk ◽  
O. Hevko ◽  
...  
Keyword(s):  
Research Process ◽  
Control Mode ◽  
Automated Control ◽  
Resonance Vibrations ◽  
Wide Range ◽  
Measurement Results ◽  
Medium System ◽  
Angular Velocities ◽  
Bulk Medium ◽  
Analytical Relations

The article outlines the relevance of using the principle of telescopy in the process of creation screw conveyors, which nowadays are folded to obtain significant lengths, which makes their designs expensive and structurally unreasonably complicated. It has been shown an experimental equipment, which provides measurement results of the research process in a wide range with high accuracy in an automated control mode with the necessary data capture. Based on the constructed mathematical model, the dependences of the angular perturbation velocity on the physicomechanical and geometric parameters of the «telescopic screw — bulk medium» system have been obtained. Because of analytical relations describing the laws of variation of characteristic parameters for its oscillation resonance case have been received. It has been proved that for resonant oscillations, when there are significant angular velocities of rotation, the natural frequency of the bending oscillations is smaller and at the same time the amplitude of the transition through the resonance is smaller. The results of the amplitude of the transverse oscillations of the system for different values of the angular velocity of rotation in time during the transition through the internal resonance, which largely depends on the physicomechanical and geometric characteristics of the motion of the medium, have been presented.

Feedback as a form of control in a technogenic educational environment

2020 ◽  
pp. 44-49
Author(s):  
I. V. Kharlamenko ◽  
V. V. Vonog
Keyword(s):  
Foreign Language ◽  
Peer Assessment ◽  
Educational Environment ◽  
Educational Process ◽  
Mobile Technologies ◽  
Independent Learning ◽  
Bring Your Own Device ◽  
Self Assessment ◽  
Automated Control ◽  
Wide Range

The article is devoted to control and feedback in foreign language teaching in a technogenic environment. The educational process is transformed in terms of the implementation and active use of digital technologies. ICT-rich environment provides new models of interaction between the teacher, students and digital tools. It also enriches the diversity of tasks and expands the range of possible forms of control and feedback. According to the authors, automated evaluation takes place both in out-of-classroom activities and directly in the classroom using Bring Your Own Device technology (BYOD). Automated control contributes to the intensity of the educational process. It provides all the participants with an opportunity to choose a convenient mode of work and get instant feedback, thereby allowing self-assessment and self-reflection of their own actions. When teaching foreign languages, special attention should be paid to chatbot technology. Chatbots imitate human actions and are able to perform standard repetitive tasks. The growing popularity of bots is explained by a wide range of usage spheres and the ability to integrate chatbots into social networks and mobile technologies. In the technogenic educational environment, ICT can be the basis for interaction, co-editing and peer assessment in collaborative projects. In this case, students receive feedback not only from the teacher, but also from other students, which increases the motivation for independent learning. Thus, automated control, self-assessment and peer assessment can both identify problem areas for each student and design an individual learning path, which increases the effectiveness of learning a foreign language.

Presenting Medical Statistics from Proposal to Publication

2017 ◽  
Author(s):  
Janet L. Peacock ◽  
Sally M. Kerry ◽  
Raymond R. Balise
Keyword(s):  
Journal Article ◽  
Real Data ◽  
Research Process ◽  
Research Report ◽  
Medical Statistics ◽  
Extensive Experience ◽  
Wide Range ◽  
Sample Size Calculations ◽  
The Usa ◽  
The Uk

Presenting Medical Statistics from Proposal to Publication (second edition) aims to show readers how to conduct a wide range of statistical analyses from sample size calculations through to multifactorial regressions that are needed in the research process. The second edition of ‘Presenting’ has been revised and updated and now includes Stata, SAS, SPSS, and R. The book shows how to interpret each computer output and illustrates how to present the results and accompanying text in a format suitable for a peer-reviewed journal article or research report. All analyses are illustrated using real data and all programming code, outputs, and datasets used in the book are available on a website for readers to freely download and use. ‘Presenting’ includes practical information and helpful tips for software, all statistical methods used, and the research process. It is written by three experienced biostatisticians, Janet Peacock, Sally Kerry, and Ray Balise from the UK and the USA, and is born out of their extensive experience conducting collaborative medical research, teaching medical students, physicians, and other health professionals, and providing researchers with advice.

scholarly journals Metamaterial Cell-Based Superstrate towards Bandwidth and Gain Enhancement of Quad-Band CPW-Fed Antenna for Wireless Applications

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 457 ◽  
Author(s):  
Samir Salem Al-Bawri ◽  
Md Shabiul Islam ◽  
Hin Yong Wong ◽  
Mohd Faizal Jamlos ◽  
Adam Narbudowicz ◽  
...  
Keyword(s):  
Refractive Index ◽  
Wave Propagation ◽  
Negative Refractive Index ◽  
Coplanar Waveguide ◽  
Ring Resonators ◽  
Wireless Applications ◽  
Gain Enhancement ◽  
Wide Range ◽  
Measurement Results ◽  
High Bandwidth

A multiband coplanar waveguide (CPW)-fed antenna loaded with metamaterial unit cell for GSM900, WLAN, LTE-A, and 5G Wi-Fi applications is presented in this paper. The proposed metamaterial structure is a combination of various symmetric split-ring resonators (SSRR) and its characteristics were investigated for two major axes directions at (x and y-axis) wave propagation through the material. For x-axis wave propagation, it indicates a wide range of negative refractive index in the frequency span of 2–8.5 GHz. For y-axis wave propagation, it shows more than 2 GHz bandwidth of near-zero refractive index (NZRI) property. Two categories of the proposed metamaterial plane were applied to enhance the bandwidth and gain. The measured reflection coefficient (S11) demonstrated significant bandwidths increase at the upper bands by 4.92–6.49 GHz and 3.251–4.324 GHz, considered as a rise of 71.4% and 168%, respectively, against the proposed antenna without using metamaterial. Besides being high bandwidth achieving, the proposed antenna radiates bi-directionally with 95% as the maximum radiation efficiency. Moreover, the maximum measured gain reaches 6.74 dBi by a 92.57% improvement compared with the antenna without using metamaterial. The simulation and measurement results of the proposed antenna show good agreement.

ANALYSIS OF THE QUESTIONNAIRE FOR ASSESSING THE LEADERSHIP QUALITIES OF STUDENTS

2019 ◽  
Vol 5 ◽  
pp. 430
Author(s):  
Anatoly Maslak
Keyword(s):  
Latent Variables ◽  
Latent Variable ◽  
Theory Of Measurement ◽  
Interval Scale ◽  
Leadership Qualities ◽  
Wide Range ◽  
Measurement Results ◽  
Measuring Tool ◽  
Better Than

The quality of the questionnaire as a measuring tool largely determines the relevance of the results. The aim of the work is to analyze the quality of the questionnaire as a measuring tool used to evaluate the latent variable "leadership qualities of students". The study was conducted within the framework of the theory of measurement of latent variables, which has important advantages. First of all, the latent variable is determined operationally, through a set of indicators (questionnaire items), the more indicators, the higher the accuracy of the latent variable measurement. The latent variable and indicators are measured on the same interval scale in logits. This allows the use of a wide range of statistical procedures for the analysis of measurement results. The analysis of the following aspects of the quality of the questionnaire as a measuring tool: the presence of extreme indicators in the test, the compatibility of a set of indicators, the compliance of the questionnaire to the level of students on the measured latent variable, the uniformity of the distribution of indicators on the interval scale. The indicators that differentiate students with high and low levels of leadership qualities better than others are highlighted. Recommendations on the adjustment of the questionnaire as a measuring tool for assessing the leadership qualities of students are given. 

Methods of studying sighting axis oscillations when observing the Earth’s surface from the Russian segment of the International Space Station

2020 ◽  
Author(s):  
R.A. Evdokimov ◽  
V.Yu. Tugaenko ◽  
A.V. Smirnov
Keyword(s):  
International Space Station ◽  
Measurement Errors ◽  
Space Station ◽  
Guidance System ◽  
International Space ◽  
Scientific Equipment ◽  
Measurement Results ◽  
Angular Velocities ◽  
Long Term Trends

The study introduces a method for determining the characteristics of long-period oscillations of the International Space Station structure by analyzing the displacement of the sighting axis of scientific equipment relative to the calculated position when observing the Earth’s surface from the Russian segment. The technique makes it possible to identify long-term oscillations through noise caused by high-frequency oscillations and measurement errors, as well as long-term trends associated with a change in the orientation of the station. The work was carried out as part of the first stage of the Pelican space experi-ment to develop the technology of wireless energy transmission in space. After processing the measurement results performed in the experiment sessions, it was possible to determine the maximum values of the amplitudes and angular velocities of the displacement of the sighting axis in order to clarify the requirements for the guidance system of scientific equipment used in the subsequent stages of the experiment.

Experimental determination of thermal conductivity of composite materials in a wide range of values at room temperature

2019 ◽  
Author(s):  
A.N. Chistov ◽  
M.Yu. Kladov ◽  
I.B. Pronin ◽  
A.S. Smirnov
Keyword(s):  
Thermal Conductivity ◽  
Composite Materials ◽  
Room Temperature ◽  
Measurement Procedure ◽  
Thermal Mode ◽  
Wide Range ◽  
Measurement Results ◽  
Transfer Problems ◽  
Range Of Values

In developing new composite materials and solving heat transfer problems, the thermal conductivity is an important characteristic that must be reliably determined. This often requires samples of the smallest dimensions, which is relevant for the production of pilot batches of material, as well as if they are taken directly from the product, when the amount of material is very limited. Most common methods for determining thermal conductivity require samples of relatively large sizes. To measure thermal conductivity on small-sized samples, an upgraded benchtop instrument is introduced. The instrument uses the relative method of longitudinal heat flux, which consists in a comparative measurement of a sample located between the heater and the standard in a stationary thermal mode. This paper presents the instrument design details, the requirements for the samples, explains the calibration features and the measurement procedure. The measurement results in a number of composite materials, as well as in materials with well-studied properties are analyzed. Findings show that the error of determining the thermal conductivity on a modernized instrument does not exceed several percent.

Overview: Damage in brittle layer structures from concentrated loads

2002 ◽  
Vol 17 (12) ◽  
pp. 3019-3036 ◽  
Author(s):  
Brian R. Lawn ◽  
Yan Deng ◽  
Pedro Miranda ◽  
Antonia Pajares ◽  
Herzl Chai ◽  
...  
Keyword(s):  
Damage Mechanics ◽  
Limiting Factors ◽  
Damage Initiation ◽  
Layer Structures ◽  
Brittle Layer ◽  
Wide Range ◽  
Damage Process ◽  
Analytical Relations ◽  
System Variables ◽  
Process Damage

In this article, we review recent advances in the understanding and analysis of damage initiation and evolution in laminate structures with brittle outerlayers and compliant sublayers in concentrated loading. The relevance of such damage to lifetime-limiting failures of engineering and biomechanical layer systems is emphasized. We describe the results of contact studies on monolayer, bilayer, trilayer, and multilayer test specimens that enable simple elucidation of fundamental damage mechanics and yet simulate essential function in a wide range of practical structures. Damage processes are observed usingpost mortem(“bonded-interface”) sectioning and directin situviewing during loading. The observations reveal a competition between damage modes in the brittle outerlayers—cone cracks or quasiplasticity at the top (near-contact) surfaces and laterally extending radial cracks at the lower surfaces. In metal or polymeric support layers, yield or viscoelasticity can become limiting factors. Analytical relations for the critical loads to initiate each damage mode are presented in terms of key system variables: geometrical (layer thickness and indenter radius); material (elastic modulus, strength and toughness of brittle components, hardness of deformable components). Such relations provide a sound physical basis for the design of brittle layer systems with optimal damage thresholds. Other elements of the damage process—damage evolution to failure, crack kinetics (and fatigue), flaw statistics, and complex (tangential) loading—are also considered.

Study of Microstructure, Texture and Residual Stress in Asymmetrically Rolled Titanium

2014 ◽  
Vol 777 ◽  
pp. 1-6 ◽  
Author(s):  
Marcin Wronski ◽  
Krzysztof Wierzbanowski ◽  
Lucjan Pytlik ◽  
Brigitte Bacroix ◽  
Mirosław Wróbel ◽  
...  
Keyword(s):  
Residual Stress ◽  
X Ray Diffraction ◽  
Asymmetric Rolling ◽  
Rolling Mills ◽  
X Ray ◽  
Wide Range ◽  
Strong Shear ◽  
Angular Velocities ◽  
Ebsd Technique ◽  
Titanium Grade

Asymmetric rolling is a promising forming technique offering numerous possibilities of material properties modification and the improvement of technological process parameters. This geometry of deformation is relatively easy to implement on existing industrial rolling mills. Moreover, it can provide large volume of a material with modified properties. The study of microstructure, crystallographic texture and residual stress in asymmetrically rolled titanium (grade 2) is presented in this work. The above characteristics were examined using EBSD technique and X-ray diffraction. The rolling asymmetry was realized using two identical rolls, driven by independent motors, rotating with different angular velocities ω1 and ω2. This ensured a wide range of rolling asymmetry: A=ω1/ω2. It was found that a strong shear stress induced in the asymmetrically rolled material allowed to obtain a microstructure refinement, texture homogenization and lowering of residual stress.

scholarly journals Comparison of 6 Diode and 6 Transistor Mixers Based on Analysis and Measurement

2016 ◽  
Vol 2016 ◽  
pp. 1-17 ◽  
Author(s):  
J. Ladvánszky ◽  
K. M. Osbáth
Keyword(s):  
Field Effect Transistors ◽  
Input Power ◽  
Bipolar Transistors ◽  
Large Signal ◽  
Design Environment ◽  
Third Order ◽  
The Third ◽  
Wide Range ◽  
Measurement Results ◽  
Versus Input

Our goal is to overview semiconductor mixers designed for good large signal performance. Twelve different mixers were compared utilizing pn diodes, bipolar transistors, and/or junction field effect transistors. The main aspect of comparison is the third-order intercept point (IP3), and both circuit analysis and measurement results have been considered. IP3 has been analyzed by the program AWR (NI AWR Design Environment) and measured by two-tone test (Keysight Technologies). We provide three ways of improvement of large signal performance: application of a diplexer at the RF port, reduction of DC currents, and exploiting a region of RF input power with infinite IP3. In addition to that, our contributions are several modifications of existing mixers and a new mixer circuit (as illustrated in the figures). It is widely believed that the slope of the third-order intermodulation product versus input power is always greater than that of the first-order product. However, measurement and analysis revealed (as illustrated in the figures) that the two lines may be parallel over a broad range of input power, thus resulting in infinite IP3. Mixer knowledge may be useful for a wide range of readers because almost every radio contains at least one mixer.

A Design of Large-Scale Speed Modulation in Hydraulic Cylinder and its Application

2010 ◽  
Vol 97-101 ◽  
pp. 3718-3721
Author(s):  
Jun Xiao ◽  
Yong Gan ◽  
Wen Ma
Keyword(s):  
Large Scale ◽  
Dimensional Accuracy ◽  
Hydraulic Cylinder ◽  
Control Mode ◽  
Precise Position ◽  
Speed Modulation ◽  
Wide Range ◽  
Speed Range ◽  
Wide Speed Range

This paper presents a hydraulic controlling mode to drive a hydraulic differential cylinder with a wide range of speed options. Two different pumps are used to control the cylinder on both sides of the oil chambers by adjusting speed and direction of the pumps. To accomplish a precise position for the cylinder among the wide speed range, the pumps are driven by two servo motors. This control mode is applied on a wheelset assembly machine to ensure dimensional accuracy of pressed wheels on an axle.

Sign in / Sign up

Export Citation Format

Share Document