Instabilities of soft dielectrics

2019 ◽  
Vol 377 (2144) ◽  
pp. 20180077 ◽  
Author(s):  
Luis Dorfmann ◽  
Ray W. Ogden
Keyword(s):  
Applied Mathematics ◽  
Numerical Results ◽  
Modern Theory ◽  
Theme Issue ◽  
Flexible Electrodes ◽  
Thin Walled Tube ◽  
Soft Dielectrics ◽  
Comparison Of The Results ◽  
Recent Review Article

The basic modern theory of nonlinear electroelasticity and its use in the formulation of constitutive laws governing the behaviour of dielectric elastomer materials was summarized in a recent review article by Dorfmann & Ogden (Dorfmann & Ogden 2017 Proc. R. Soc. A 473 , 20170311 ( doi:10.1098/rspa.2017.0311 )). The theory is used, in particular, to analyse the behaviour of transducer devices such as actuators and sensors. Important considerations for the design and effective functioning of such devices are the issues of material and geometric instabilities. Following on from the above-cited work, the present paper provides a detailed account of the types of instabilities that arise for some of the geometries used in transducer devices and the theory that is adopted for the analysis of such instabilities. The theory is then used in two illustrative examples: (i) determination of instabilities of a thin electroelastic plate with flexible electrodes attached to its major surfaces, in particular comparison of the results for the so-called Hessian approach and a general incremental bifurcation analysis in respect of an equibiaxially stretched plate, with numerical results presented for a Gent electroelastic model; (ii) a general analysis of axi-symmetric bifurcation from a circular cylindrical configuration of a thin-walled tube of an electroelastic material with flexible electrodes on its curved surfaces, illustrated by numerical results for neo-Hookean and Gent electroelastic models. This article is part of the theme issue ‘Rivlin's legacy in continuum mechanics and applied mathematics’.

Features of phosphorus-calcium metabolism in children with neurogenic disorders of urination

2020 ◽  
Vol 24 (1) ◽  
pp. 45-50
Author(s):  
Yu. F. Lobanov ◽  
D. Y. Latyshev ◽  
Ya. F. Zverev ◽  
N. A. Tekuteva ◽  
N. M. Mikheeva
Keyword(s):  
Connective Tissue ◽  
Calcium Metabolism ◽  
Point System ◽  
Industry Standards ◽  
Muscular Dysfunction ◽  
Connective Tissue Dysplasia ◽  
Calcium And Phosphorus ◽  
Comparison Of The Results ◽  
Neurogenic Disorders

THE AIM: To study the characteristics of phosphorus-calcium metabolism in patients with neurogenic disorders of urination, taking into account the severity of the manifestations of connective tissue dysplasia. PATIENTS AND METHODS. The study included 90 children, including 60 children with neuro-muscular dysfunction of the bladder (NMDB) and 30 children with enuresis from the age of 5 to 15 years. The diagnosis was established based on a comprehensive examination and according to industry standards. Connective tissue dysplasia was diagnosed in children with the detection of 6 or more small external or visceral manifestations involving 3 or more organs from different systems. Assessment of the severity (severity) of connective tissue dysplasia was carried out according to the point system proposed by T.I. Kadurina et al. Each group was divided into subgroups depending on the severity of the manifestations of connective tissue dysplasia. The determination of the level of calcium and phosphorus in the blood and urine, as well as the calculation of the calcium-creatinine coefficient followed by a comparison of the results in these groups and subgroups. To assess the significance of differences, the Mann-Whitney test was calculated, p <0.05 was considered significant. RESULTS. he level of calcium and phosphorus in the urine was slightly higher in children with enuresis, especially in the morning portion of urine, where the concentration of calcium was 26% higher than in patients with NMDB. At the same time, the value of calcium /creatinine coefficient was significantly higher in the group of patients with enuresis and was 2 times higher than the normative indicators, which indicates the importance of hypercalciuria in the development of enuresis. СONCLUSION. According to the obtained data, the severity of calciuria, determined by the value of the calcium-creatinine coefficient, is significantly higher in patients with enuresis than with NMDB.

scholarly journals New Kinetic Spectrophotometric Method for Determination of Folic Acid in Pharmaceutical Formulations

2015 ◽  
Vol 50 ◽  
pp. 169-178
Author(s):  
Mouhammed Khateeb ◽  
Basheer Elias ◽  
Fatema Al Rahal
Keyword(s):  
Folic Acid ◽  
Spectrophotometric Method ◽  
Pharmaceutical Formulations ◽  
Fixed Time ◽  
Rate Data ◽  
Sulfuric Acid Medium ◽  
Significant Difference ◽  
Kinetic Spectrophotometric ◽  
Comparison Of The Results

A simple and sensitive kinetic spectrophotometric method has been developed for the determination of folic acid (FA) in bulk and pharmaceutical Formulations. The method is based on the oxidation of FA by Fe (III) in sulfuric acid medium. Fe (III) subsequently reduces to Fe (II) which is coupled with potassium ferricyanide to form Prussian blue. The reaction is followed spectrophotometrically by measuring the increase in absorbance at λmax 725 nm. The rate data and fixed time methods were adopted for constructing the calibration curves. The linearity range was found to be 1–20 μg mL-1 for each method. The correlation coefficient was 0.9978 and 0.9993, and LOD was found to be 0.91 and 0.09 μg mL-1 for rate data and fixed time methods, respectively. The proposed method has been successfully applied to the determination of FA in formulations with no interference from the excipients. Statical comparison of the results shows that there is no significant difference between the proposed and pharmacopoeial methods

scholarly journals Combat horting in the method of education of physical culture and fundamentals of health and determination of working capacity of schoolchildren and student athletes

2021 ◽  
pp. 45-54
Author(s):  
Eduard Yeromenko ◽  
Maksym Doroshenko
Keyword(s):  
Educational Process ◽  
Theory And Practice ◽  
Educational Activity ◽  
Scientific Article ◽  
Physical Culture ◽  
Modern Theory ◽  
Working Capacity ◽  
Age Features ◽  
And Training

This scientific article reveals the methods of education of physical culture and basics of health and determination of working capacity of athletes of combat horting of pupil and student age, features of direction and volumes of training load. The publication analyzes the relationship between combat horting and health for schoolchildren and students during their education and training in sports sections of general secondary and higher education. Every year the National Federation of Combat Horting of Ukraine raises more and more problems of health-improving orientation of the educational process by means of sports. During the years of perestroika and reforms, scientists, teachers and leaders of the sports federation, educational sphere organized and conducted many serious studies, obtained many valuable sports, philosophical, socio-economic and psychological-pedagogical results, developed important concepts and recommendations, implemented a number of practical measures in the field of improvement of educational and training process, its adaptation to new conditions of educational activity in Ukraine. The analysis of methods of education of physical culture and basics of health of athletes of combat horting, the analysis and definition of their working capacity, value potential of combat horting and new ways of its development by a society and the person, and also pedagogical values of the trainer on combat horting, allows to receive ideas approaches formed in the modern theory and practice of combat horting.

Determination of the energy in body and surface waves

1959 ◽  
Vol 49 (1) ◽  
pp. 1-10
Author(s):  
John De Noyer
Keyword(s):  
Surface Waves ◽  
Seismic Waves ◽  
Numerical Results

Abstract Part II of this paper is concerned with the application of the methods for estimating the energy in seismic waves that were presented in Part I. Numerical results for the energy in the various phases of several earthquakes have been obtained.

Number of rational points of elliptic curves

2021 ◽  
pp. 2250017
Author(s):  
Viliam Ďuriš ◽  
Timotej Šumný
Keyword(s):  
Elliptic Curve ◽  
Elliptic Curves ◽  
Current Knowledge ◽  
American Mathematical Society ◽  
Rational Points ◽  
Modern Theory ◽  
Cambridge University ◽  
Weil Theorem ◽  
A Finite Group

In the modern theory of elliptic curves, one of the important problems is the determination of the number of rational points on an elliptic curve. The Mordel–Weil theorem [T. Shioda, On the Mordell–Weil lattices, Comment. Math. University St. Paul. 39(2) (1990) 211–240] points out that the elliptic curve defined above the rational points is generated by a finite group. Despite the knowledge that an elliptic curve has a final number of rational points, it is still difficult to determine their number and the way how to determine them. The greatest progress was achieved by Birch and Swinnerton–Dyer conjecture, which was included in the Millennium Prize Problems [A. Wiles, The Birch and Swinnerton–Dyer conjecture, The Millennium Prize Problems (American Mathematical Society, 2006), pp. 31–44]. This conjecture uses methods of the analytical theory of numbers, while the current knowledge corresponds to the assumptions of the conjecture but has not been proven to date. In this paper, we focus on using a tangent line and the osculating circle for characterizing the rational points of the elliptical curve, which is the greatest benefit of the contribution. We use a different view of elliptic curves by using Minkowki’s theory of number geometry [H. F. Blichfeldt, A new principle in the geometry of numbers, with some applications, Trans. Amer. Math. Soc. 15(3) (1914) 227–235; V. S. Miller, Use of elliptic curves in cryptography, in Proc. Advances in Cryptology — CRYPTO ’85, Lecture Notes in Computer Science, Vol. 218 (Springer, Berlin, Heidelberg, 1985), pp. 417–426; E. Bombieri and W. Gubler, Heights in Diophantine Geometry, Vol. 670, 1st edn. (Cambridge University Press, 2007)].

scholarly journals Extractive Spectrophotometric Methods for Determination of Zolmitriptan in Tablets

2007 ◽  
Vol 90 (5) ◽  
pp. 1237-1241 ◽  
Author(s):  
Zeynep Aydogmus ◽  
Ipek Inanli
Keyword(s):  
High Performance ◽  
Correlation Coefficients ◽  
Bromothymol Blue ◽  
Chromatography Method ◽  
Statistical Comparison ◽  
Spectrophotometric Methods ◽  
Accuracy And Precision ◽  
Liquid Chromatography Method ◽  
Comparison Of The Results

Abstract Two simple and sensitive extractive spectrophotometric methods have been developed for determination of zolmitriptan (ZTP) in tablets. These methods are based on the formation of yellow ion-pair complexes between ZTP and tropaeolin OO (TPOO) and bromothymol blue (BTB) in citratephosphate buffer of pH 4.0 and 6.0, respectively. The formed complexes were extracted with dichloromethane and measured at 411.5 and 410 nm for TPOO and BTB, respectively. The best conditions of the reactions were studied and optimized. Beer's law was obeyed in the concentration ranges of 220 and 1.517 g/mL with molar absorptivities of 1.42 104 and 1.60 104 L/mol/cm for the TPOO and BTB methods, respectively. Correlation coefficients were 0.9998 and 0.9999 for TPOO and BTB methods, respectively. Limits of detection of the TPOO and BTB methods were 0.341 and 0.344 g/mL, respectively, and the limits of quantitation were 1.034 and 1.051 g/mL, respectively. Sandell's sensitivity and stability constant were also calculated. The proposed methods have been applied successfully for the analysis of the drug in its dosage forms. No interference was observed from excipients present in tablets. Statistical comparison of the results with those obtained by a high-performance liquid chromatography method showed excellent agreement and indicated no significant differences in accuracy and precision.

scholarly journals Experimental and Numerical Study on Dynamics of Two Footbridges with Different Shapes of Girders

2020 ◽  
Vol 10 (13) ◽  
pp. 4505 ◽  
Author(s):  
Anna Banas ◽  
Robert Jankowski
Keyword(s):  
Natural Vibration ◽  
Numerical Study ◽  
Numerical Results ◽  
Vibration Exciter ◽  
Structural Vibrations ◽  
Impulse Load ◽  
Different Shapes ◽  
Comfort Criteria ◽  
Good Agreement

The paper presents the experimental and numerical results of the dynamic system identification and verification of the behavior of two footbridges in Poland. The experimental part of the study involved vibration testing under different scenarios of human-induced load, impulse load, and excitations induced by vibration exciter. Based on the results obtained, the identification of dynamic parameters of the footbridges was performed using the peak-picking method. With the impulse load applied to both structures, determination of their natural vibration frequencies was possible. Then, based on the design drawings, detailed finite element method (FEM) models were developed, and the numerical analyses were carried out. The comparison between experimental and numerical results obtained from the modal analysis showed a good agreement. The results also indicated that both structures under investigation have the first natural bending frequency of the deck in the range of human-induced excitation. Therefore, the risk of excessive structural vibrations caused by pedestrian loading was then analysed for both structures. The vibration comfort criteria for both footbridges were checked according to Sétra guidelines. In the case of the first footbridge, the results showed that the comfort criteria are fulfilled, regardless of the type of load. For the second footbridge, it was emphasized that the structure meets the assumptions of the guidelines for vibration severability in normal use; nevertheless, it is susceptible to excitations induced by synchronized users, even in the case of a small group of pedestrians.

Elastic Layer Pressed Against a Half Space

1974 ◽  
Vol 41 (3) ◽  
pp. 703-707 ◽  
Author(s):  
K. C. Tsai ◽  
J. Dundurs ◽  
L. M. Keer
Keyword(s):  
Eigenvalue Problem ◽  
Integral Equations ◽  
Half Space ◽  
Elastic Layer ◽  
Numerical Results ◽  
Fredholm Integral Equations ◽  
Auxiliary Functions ◽  
Receding Contact ◽  
Two Bodies

The paper considers the elastic layer which is pressed against a half space by loads that are not necessarily symmetric about the center of the loaded region. It is shown that the receding contact between the two bodies can be treated by means of superposition, leading to two homogeneous Fredholm integral equations for auxiliary functions that are directly related to the contact tractions. The determination of the extent of contact and the shift between the load and contact intervals can be viewed as an eigenvalue problem of the homogeneous integral equations. Specific numerical results are given for two types of triangular loads, and a comparison is made with certain symmetric loads.

Characteristics of a Self-Lubricated Stepped Thrust Pad of Infinite Width With Compressible Lubricant

1959 ◽  
Vol 81 (2) ◽  
pp. 135-145 ◽  
Author(s):  
Kikuo C. Kochi
Keyword(s):  
Optimum Design ◽  
Practical Interest ◽  
Numerical Data ◽  
Numerical Results ◽  
Design Parameters ◽  
Analytic Expressions ◽  
Thrust Pad ◽  
Compressible Lubricant

Harrison’s equation for the pressure in a gas-lubricated bearing of infinite width is solved for a thrust pad with stepped configuration. Analytic expressions for the pressure and load are developed. Numerical results are presented graphically. The analytic expressions together with the numerical data permit most of those characteristics of the stepped pad of practical interest to be completely determinable. Determination of optimum design parameters is given by a pair of graphs.

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