scholarly journals Some Stochastic Specific Features of Concrete and Reinforced Concrete Carbonization

2019 ◽  
Vol 18 (2) ◽  
pp. 127-136
Author(s):  
S. N. Osipov ◽  
A. V. Zakharenko ◽  
V. M. Chik
Keyword(s):  
Extreme Values ◽  
Protective Layer ◽  
Variation Coefficient ◽  
Stochastic Estimation ◽  
Average Value ◽  
Concrete Layer ◽  
Residual Thickness ◽  
Multiple Measurements ◽  
Normal Law ◽  
Corrosion Of Steel

Reliable calculation of concrete carbonization development is considered as a basis of forecasting corrosion of steel reinforcement and longevity of reinforced construction structures. Investigation results for stochastic specific features of carbonization in a protective concrete layer or its residual thickness in reinforced structures operating in airspace have been obtained for the last 20 years. In this case it is recommended for simulation of a protective concrete layer to use a normal law of distribution and a histogram which looks like distribution of extreme values is recommended for its residual thickness. Stochastic estimation for multiple measurements (1211 results excluding obviously unsuccessful ones) has made it possible to determine rather large values of variation coefficient (maximum values up to 0.34 with average index about 0.19) for indices of initial carbonization for С12/15−С20/25 concrete grades. At the same time these variation coefficients for С25/30 and С30/37 concrete grades have decreased up to 0.15 and 0.11, respectively. It has been established that density of distribution for random carbonization values of С12/15−С18/22.5 concrete grades being operated under conditions of agricultural premises with high aggressive environment corresponds, as a rule, to a normal law after excluding evidently unwanted values. In this connection use of maximum and minimum values of concrete carbonization in selections for estimation of variation coefficients differs from determination for the whole selection and it requires a corresponding correction. While operating С12/15−С18/22.5 concrete grades under conditions of agricultural premises in the period of 10−40 years average values of variation coefficients remain approximately constant with fluctuation up to ±0.01 with average value of 0.11−0.12. Spread in some variation coefficient values for concrete carbonization is decreasing from two to 1.25-fold within this period of time and later on it likely becomes stabilized. As a whole while determining duration of concrete protective layer carbonization it is necessary to take into account not only stochasticity of concrete protective layer and carbonization rate but also random values of concrete carbonization at specific carbonization rate and depth.

The Merits of Confidence Intervals Relative to Hypothesis Testing

1992 ◽  
Vol 13 (9) ◽  
pp. 553-555 ◽  
Author(s):  
Leon F. Burmeister ◽  
David Bimbaum ◽  
Samuel B. Sheps
Keyword(s):  
Hypothesis Testing ◽  
Confidence Intervals ◽  
Null Hypothesis ◽  
Finite Population ◽  
Extreme Values ◽  
Statistical Tests ◽  
Point Estimate ◽  
Distributed Data ◽  
Average Difference ◽  
Average Value

A variety of statistical tests of a null hypothesis commonly are used in biomedical studies. While these tests are the mainstay for justifying inferences drawn from data, they have important limitations. This report discusses the relative merits of two different approaches to data analysis and display, and recommends the use of confidence intervals rather than classic hypothesis testing.Formulae for a confidence interval surrounding the point estimate of an average value take the form: d= ±zσ/√n, where “d” represents the average difference between central and extreme values, “z” is derived from the density function of a known distribution, and “a/-∨n” represents the magnitude of sampling variability. Transposition of terms yields the familiar formula for hypothesis testing of normally distributed data (without applying the finite population correction factor): z = d/(σ/√n).

Cumulative Damage in Fatigue—A Design Method Based on the S-N Curve

1957 ◽  
Vol 61 (559) ◽  
pp. 485-491 ◽  
Author(s):  
John C. Levy
Keyword(s):  
Stress Level ◽  
Extreme Values ◽  
Design Method ◽  
High Stress ◽  
Fatigue Tests ◽  
Three Dimensions ◽  
Average Value ◽  
Straight Line ◽  
Wide Range ◽  
Pull Tests

SummaryIt is suggested that a convenient way of presenting the results of fatigue tests in which two different stress amplitudes are applied alternately is to plot log N against log (n1/n) where N is the total cycles to failure and (n1/n) is the fraction of cycles run at the high stress.With these co-ordinates, a simple geometrical construction gives a safe design method for the two-stress level system using only the conventional S-N curve and the value of (n1/n) expected to be encountered in service. If N1 and N2 are the lives at the high and low stresses as read from the S-N curve, one point may be plotted at (log N1, 0) since this represents the programme when all cycles are at the high stress. On the assumption, shown to be justified, that less than one cycle of high stress per 10,000 total cycles would not significantly affect the life at the low stress, a second point is plotted at (log N2, 4). The straight line joining these two points is always found to predict safe values of N for any value of (n1/n).This conclusion is checked against a wide range of experimental results taken from six different sources in the literature covering rotating-bending and push-pull tests, ferrous and non-ferrous metals, any order of stressing and length of programme cycle from 50 up to 5 million. This last feature means that the length of the programme cycle in service need not be known. All that is required is the proportion in which the two stress amplitudes are mixed. The average value of the ratio (experimental life/predicted life) for the data examined is 1·8, the extreme values being 1 and 56. By plotting in three dimensions an equation is also developed for the three-stress level spectrum and a suggestion is made for an extension of the method to multiple stress levels.

scholarly journals Concrete Protective Layer Cracking Caused by Non-Uniform Corrosion of Reinforcements

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4245 ◽  
Author(s):  
Lu Zhang ◽  
Ditao Niu ◽  
Bo Wen ◽  
Daming Luo
Keyword(s):  
Radial Displacement ◽  
Concrete Strength ◽  
Protective Layer ◽  
Concrete Cover ◽  
Uniform Corrosion ◽  
Reinforcement Corrosion ◽  
Concrete Cracking ◽  
Principal Tensile Stress ◽  
Cover Thickness ◽  
Corrosion Of Steel

The volume expansion of reinforcement corrosion products resulting from the corrosion of steel reinforcement embedded into concrete causes the concrete’s protective layer to crack or spall, reducing the durability of the concrete structure. Thus, it is necessary to analyze concrete cracking caused by reinforcement corrosion. This study focused on the occurrence of non-uniform reinforcement corrosion in a natural environment. The characteristics of the rust layer were used to deduce the unequal radial displacement distribution function of concrete around both angular and non-angular bars. Additionally, the relationship between the corrosion ratio and the radial displacement of the concrete around the bar was established quantitatively. Concrete cracking due to the non-uniform corrosion of reinforcements was simulated using steel bars embedded in concrete that were of uneven displacement because of rust expansion. The distribution of the principal tensile stress around the bar was examined. A formula for calculating the critical radial displacement at the point when cracking began was obtained and used to predict the corrosion ratio of the concrete cover. The determined analytical corrosion ratio agreed well with the test result. The effect factor analysis based on the finite element method indicated that increasing the concrete strength and concrete cover thickness delays concrete cracking and that the adjacent rebar causes the stress superposition phenomenon.

scholarly journals Method for constructing estimates of accuracy of measuring equipment based on Bayesian scientific approach

2019 ◽  
Vol 135 ◽  
pp. 01070
Author(s):  
Rustam Khayrullin
Keyword(s):  
New Technologies ◽  
Statistical Data ◽  
A Priori ◽  
Small Scale ◽  
Average Value ◽  
Scientific Approach ◽  
Distribution Laws ◽  
Technical Systems ◽  
Normal Law ◽  
Self Learning

Before putting new unique samples of technical systems into commercial operation, as well as before introducing new technologies into production, as a rule, all kinds of tests are carried out. Small and very small volume of statistical data during testing is a characteristic feature of unique and small-scale products and technical systems. Therefore, the problem of constructing effective statistical estimates with a limited amount of statistical information is an important practical problem. The article proposes the development of the Bayesian approach to the construction of point and interval estimates of the parameters of the known distribution laws. The joint use of a priori and posterior information in the processing of statistical data of a limited volume can significantly increase the reliability of the result. As an example, we consider two most typical distribution laws that arise when testing new unique samples of measuring devices and equipment: normal distribution with an unknown average value and a known dispersion, as well as with an unknown average value and an unknown dispersion. It is shown that for these cases, the parameters of the distribution laws themselves are random variables and obey the normal law and gamma normal law. Recalculation formulas are obtained to refine the parameters of these laws, taking into account a posteriori information. If these formulas are applied several times successively, the process of self-learning of the system or self-tuning of the system occurs. Thus, the proposed scientific approach can find application in the development of intelligent self-learning and self-turning systems.

Validation of the framycetin sulfate determination technique by HPLC in a Framidex medicinal preparation

2020 ◽  
Vol 86 (6) ◽  
pp. 73-78
Author(s):  
D. D. Gapparov ◽  
Z. A. Smanova ◽  
Y. V. Timchenko ◽  
A. V. Pirogov
Keyword(s):  
Medicinal Preparation ◽  
Good Manufacturing Practice ◽  
Variation Coefficient ◽  
Intermediate Precision ◽  
Average Value ◽  
Limit Of Determination ◽  
Validation Criteria ◽  
Derivatizing Agent ◽  
Order Of Magnitude

A method for determination of framycetin sulfate in a Framidex preparation (eye and ear drops) by HPLC-UV (λ = 365 nm) using 2, 4-dinitrofluorobenzene as a derivatizing agent has been developed The characteristics of analytical methods determined for the purpose of their validation and relevant criteria for the validity of validated methods with the goal of the quality control of drugs (pharmaceutical substances and drugs) are presented. According to the results of an intralaboratory experiment on the validation assessment of the method by the parameters of the specificity, limit of determination (LOD), linearity, precision and laboratory accuracy, it is shown that the LOD decreases by an order of magnitude, the correlation coefficient is not less than 0.99 correctness (average value — 97.5 – 102.5%; variation coefficient — not more than 2.0%; the confidence range should include 100% of values), convergence (variation coefficient — not more than 1.5%), intermediate precision (variation coefficient — not more than 1.5%). It is shown that the obtained values of metrological characteristics do not exceed the validation criteria and the developed method matches all the well-known requirements of GMP (Good Manufacturing Practice).

RESEARCH OF DEFORMATIONS AND OPTIMIZATION OF PARAMETERS OF DEGASATION WELLS

2020 ◽  
pp. 49-57
Author(s):  
Artem Merzlikin ◽  
◽  
Oleksandr Yaytsov ◽  
Olga Pidgurnaya ◽  
Victor Nazimko ◽  
...  
Keyword(s):  
Tensile Deformation ◽  
Underground Coal Mining ◽  
Gas Leakage ◽  
Average Value ◽  
Normal Law ◽  
Concentrated Deformation ◽  
Roof Rocks ◽  
Preparatory Work ◽  
Logarithmic Dependence ◽  
Roof Deformation

Purpose. Investigation of deformation of the mouth of the degassing well depending on the deformation of the rocks around the preparatory work Methodology. The deformation of the mouth of the degassing well as a function of deformations of the roof rocks of the preparatory workings from which the well was drilled is considered. The dependence of the required depth of well sealing on the level of methane leakage and roof deformation is established. Results. It is experimentally proved that in the zone of active shifts behind the operating lava, where the main amount of explosive methane is released from the massif, the mouths of degassing wells change and the main types of irreversible deformations take place. With the distance from the contour of the preparatory production, the distance between adjacent concentrated deformations of the wellbore increases according to the logarithmic dependence, and these deformations are distributed according to the normal law. The average value of the concentrated deformation of the degassing well is in logarithmic dependence on the displacements on the contour of the preparatory work. The tensile deformation of the degassing well axis decreases with distance from the production contour into the array. Stratification of rocks leads to gas leakage and air suction, which reduces the efficiency of degassing. Permissible concentrated deformations of the degassing wellbore should not exceed its radius. Originality. The empirical power dependence of the required length of sealing of the degassing well on the allowable leaks and displacements of the roof of the preparatory workings from which the well was drilled is established. Practical value. Methods for calculating the required sealing depth of the degassing well have been developed and measures have been proposed to increase its stability, which increase the reliability of the degassing system as a whole and help increase the safety of underground coal mining.

Kinetostatic Analysis of the Mechanism of 5-th Class by Using Vector Method

2013 ◽  
Vol 373-375 ◽  
pp. 50-53
Author(s):  
A. Abduraimov ◽  
Yuriy Drakunov ◽  
Bolat Espaev ◽  
Tatyana Zmeikova
Keyword(s):  
Angular Velocity ◽  
Dynamic Analysis ◽  
Extreme Values ◽  
Practical Importance ◽  
Constant Angular Velocity ◽  
Vector Method ◽  
Average Value ◽  
Dynamic Mechanisms ◽  
Analytical Expressions ◽  
Selection Of

In this paper, we consider the vector method of solving one of the most important problems of the dynamic analysis of mechanisms - kinetostatic analysis, which is to determine the reactions in the kinematic pairs and the balancing moment (force) on the leading link of a given law of motion of the mechanism [. This problem has a great practical importance in the selection of electro engines and in the calculation of the bearings in kinematic pairs. For example, setting the constant angular velocity of the driving link can be made kinematic and kinetostatic analysis of the mechanism and determine for all site of motion the balancing moment and the reactions in the kinematic pairs. By the average value of the balancing moment define the parameters of the electro engines and on the extreme values of the reactions produce calculation and selection of the bearings that will be installed in the hinges. In addition, knowledge of analytical expressions reactions will most clearly solve the problems of dynamic mechanisms with friction in the kinematic pairs.

scholarly journals The Average Covering Number of a Graph

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
Derya Dogan ◽  
Pinar Dundar
Keyword(s):  
Extreme Values ◽  
Covering Number ◽  
Average Value ◽  
Minimum Number ◽  
Graph Parameters

There are occasions when an average value of a graph parameter gives more useful information than the basic global value. In this paper, we introduce the concept of the average covering number of a graph (the covering number of a graph is the minimum number of vertices in a set with the property that every edge has a vertex in the set). We establish relationships between the average covering number and some other graph parameters, find the extreme values of the average covering number among all graphs of a given order, and find the average covering number for some families of graphs.

Some aspects of the X-ray structural characterization of (Ga1−x Al x As)n1(GaAs)n2/GaAs(001) superlattices: erratum

1984 ◽  
Vol 17 (5) ◽  
pp. 362-362
Author(s):  
J. Kervarec ◽  
M. Baudet ◽  
J. Caulet ◽  
P. Auvrey ◽  
J. Y. Emery ◽  
...  
Keyword(s):  
Structural Characterization ◽  
Extreme Values ◽  
Sample Zone ◽  
X Ray ◽  
Average Value ◽  
Hand Column ◽  
Right Hand ◽  
Experimental Diagram

In the paper by Kervarec, Baudet, Caulet, Auvrey, Emery & Regreny [J. Appl. Cryst. (1984). 17, 196–205], an error has been introduced. On page 202, right-hand column, the second paragraph should read: The uneven surfaces of the interfaces can be taken into account by assuming that the SL is made of a juxtaposition of perfect crystallites of the same composition x whose period varies between the extreme values of 2n 1 d 1 + 2n 2 d 2. In this hypothesis, the experimental diagram is the sum of the X-ray diagrams given by each crystallite; the value of n 1 + n 2 deduced from such a diagram is an average value in the sample zone analyzed, therefore most of the time not integer.

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