scholarly journals Model calculations of posterior reliability indicators for the proposal of the maintenance system

2018 ◽  
Vol 157 ◽  
pp. 08003 ◽  
Author(s):  
Jana Galliková ◽  
Vladimír Stuchlý ◽  
Roman Poprocký ◽  
Peter Volna
Keyword(s):  
A Priori ◽  
Weibull Model ◽  
Calculation Methods ◽  
Optimal Process ◽  
Model Calculations ◽  
Maintenance System ◽  
Reliability Indicators ◽  
Technical Practice ◽  
Reliability Methods ◽  
The Cost

Designing the content and scale of maintenance of machines and equipment by a priori and posterior reliability methods in considered crucial to reducing the cost of the machine's life cycle, maintaining high operational readiness and reducing the consequences of failures. In the presented paper, attention is paid to the analysis of the calculation methods of posterior reliability for calculation indicators of reliability and to the use of the specified Weibull model for reliability calculations. The obtained results are further developed for models of optimal process calculations to perform scheduled maintenance interventions. Calculations of the other RAMS (reliability, availability, maintainability and safety) indicators that are critical to the design of an optimal engineering design with regard to maintenance and which do not receive sufficient attention in technical practice are also assessed.

TAKING INTO CONSIDERATION OF THE MULTIPLE MODE OF THE FUNCTIONING AND CHARACTERISTICS OF THE CONTROL IN RELIABILITY MODELS OF REPLACEMENT TIME SYSTEMS

2019 ◽  
Author(s):  
Iryna Kononova
Keyword(s):  
A Priori ◽  
Telecommunication System ◽  
Structural Element ◽  
Reliability Models ◽  
Quick Recovery ◽  
Reliability Indicators ◽  
A Priori Uncertainty ◽  
Control Of Parameters ◽  
Time Systems ◽  
Time Reserve

The article evaluates the reliability indicators of telecommunication system equipment, which can be represented by multi-mode objects of continuous and episodic use with a time reserve operating under conditions of a priori uncertainty. Particular attention is paid to consideration of the process of functioning of the system with a replenished time reserve. The telecommunication system includes an object represented by one structural element and used in different modes of operation. In each mode, the object can be used continuously or episodically (the object performs tasks that occur at random times), herewith only a certain part of its equipment is operating. The restoration of the facility's operation in each mode is based on the "quick" recovery scheme ("quick" recovery means that the repair time is much less than the average working time of the element between failures). Also, some cases of the transition of an object from one mode to another are considered, and the control system operates according to the method of sequential control of parameters. In this case, the system, after waiting mode, begins to analyze the first parameter of the monitored complex, then the second and so on. After analyzing the parameters, the system enters the waiting mode. These calculated ratios allow for a comprehensive assessment of the reliability of telecommunication equipment, taking into account the totality of the main factors that significantly affect the reliability of the equipment in real conditions of operation, make it possible to solve important practical problems which arise from the improvement of existing equipment and development of existing equipment.

A weak derivative approach to optimization of threshold parameters in a multicomponent maintenance system

2001 ◽  
Vol 38 (02) ◽  
pp. 386-406 ◽  
Author(s):  
Bernd Heidergott
Keyword(s):  
Optimization Problems ◽  
Estimation Algorithm ◽  
Replacement Policy ◽  
Cost Performance ◽  
Weak Derivative ◽  
Preventive Replacement ◽  
Maintenance System ◽  
Threshold Optimization ◽  
Age Replacement ◽  
The Cost

We consider a multicomponent maintenance system controlled by an age replacement policy: when one of the components fails, it is immediately replaced; all components older than a threshold age θ are preventively replaced. Costs are associated with each maintenance action, such as replacement after failure or preventive replacement. We derive a weak derivative estimator for the derivative of the cost performance with respect to θ. The technique is quite general and can be applied to many other threshold optimization problems in maintenance. The estimator is easy to implement and considerably increases the efficiency of a Robbins-Monro type of stochastic approximation algorithm. The paper is self-contained in the sense that it includes a proof of the correctness of the weak derivative estimation algorithm.

scholarly journals ESTIMATED TRANSPORTATION COST OF LOW-TONNAGE LNG

2020 ◽  
Vol 17 (5) ◽  
pp. 130-163
Author(s):  
O. V. Tarovik ◽  
O. M. Mudrova
Keyword(s):  
Coastal Waters ◽  
Unit Cost ◽  
Transportation Cost ◽  
Model Calculations ◽  
Inland Waterways ◽  
Universal Approach ◽  
Environmental Requirements ◽  
Regression Relations ◽  
The Cost ◽  
Cost Of Transportation

Demand for low-tonnage transportation of LNG requires improved logistics. Assessing the value of all parts of the supply chain is an important component of solving the problem of optimizing transportation costs for both consumers and LNG suppliers. In connection with tightening of environmental requirements regarding bunker fuel, the task of optimizing the supply of LNG for water transport by the cost of transportation becomes particularly relevant.The objective of the study is to develop a universal approach to estimating the cost of transporting low-tonnage LNG for bunkering vessels in the Russian Federation.The research methodology is focused on the analytical method based on a system-structural approach.As part of the departmental project of the Russian Ministry of Industry and Trade «Development of  gaspowered fleet for navigation in coastal waters and inland waterways», the authors developed technical and economic models for calculating the unit cost of LNG transportation by road and water. To calculate the unit cost of LNG transportation by rail, the data of TMkarta information and reference system were used. Based on model calculations and data of TMkarta system, regression relations were obtained that allow one to determine the cost of transportation for various options of transport and technological schemes based on a limited set of parameters. An approach has also been proposed for estimating the cost of LNG transshipment. The regression ratios were tested for selected routes. As a result,conclusions were drawn about the most effective LNG transportation options.

Use of ultrasonic models in the design and validation of new NDE techniques

1986 ◽  
Vol 320 (1554) ◽  
pp. 329-340 ◽  
Keyword(s):  
Fracture Mechanics ◽  
Elastic Wave ◽  
Structural Integrity ◽  
Life Extension ◽  
Experimental Demonstration ◽  
Structural Components ◽  
Model Calculations ◽  
Model Predictions ◽  
The Cost ◽  
Theoretical Scattering

In implementing fracture mechanics based techniques for the design and life extension of structural components, it is necessary to establish the reliability with which various flaw sizes and types can be detected and characterized. Traditionally, this has been accomplished through extensive experimental demonstration programmes. This paper discusses present efforts to use model predictions to reduce the required amount of experimentation, and hence the cost, of such programmes. Formalisms whereby the extensive elastic-wave theoretical scattering effort of the last decade can be applied to practical problems are first reviewed. This is followed by several specific examples which have occurred in the nuclear and aerospace industries. The paper concludes with the identification of some important remaining theoretical problems and a discussion of possible strategies for future implementation of model calculations as tools in structural integrity programmes.

Determination of Hydraulic Permeability Based on the Measurements of Outflow

2015 ◽  
Vol 3 ◽  
pp. 105-116
Author(s):  
Jozef Kačur ◽  
Jozef Minár
Keyword(s):  
Unsaturated Flow ◽  
Dimensional Space ◽  
A Priori ◽  
Hydraulic Permeability ◽  
Infinite Dimensional ◽  
Tuning Parameters ◽  
Finite Dimensional ◽  
Partially Saturated Porous Media ◽  
The Cost

In this paper we present a method for the determination of the hydraulic permeability for flow in partially saturated porous media. The dependence of hydraulic permeability on effective saturation is not assumed to be a member of any specific finite dimensional class of functions (e.g. vanGenuchten-Mualem, Burdin-Mualem, Brook-Corey). Instead, an infinite dimensional space of functions with limited a priori assumptions (e.g. smoothness, monotonicity) is considered. Consequently, we face a more challenging problem compared to the finite-dimensional case, in which only few tuning parameters need to be determined. We consider the case of 1D unsaturated flow and assume that the data are collected at the outflow of the sample. The hydraulic permeability is determined in an iterative way. We minimize the cost functional reflecting the discrepancy between the measured and computed data. In doing so, we use the Gateaux differential to obtain the direction of the descent.

Source conditions and accuracy estimates in Tikhonov’s scheme of solving ill-posed nonconvex optimization problems

2018 ◽  
Vol 26 (4) ◽  
pp. 463-475 ◽  
Author(s):  
Mikhail Y. Kokurin
Keyword(s):  
Nonconvex Optimization ◽  
Optimization Problems ◽  
A Priori ◽  
Nonconvex Optimization Problems ◽  
Tikhonov’S Scheme ◽  
A Posteriori Parameter Choice ◽  
Ill Posed ◽  
Fréchet Differentiable ◽  
Closed Convex Set ◽  
The Cost

Abstract We obtain rate of convergence estimates for approximations delivered by Tikhonov’s scheme of solving ill-posed nonconvex optimization problems in a Hilbert space. The problems under investigation involve minimization of twice Frechet differentiable functionals given with errors on a closed convex set having a nonempty interior and smooth boundary. Assuming that the desired solution satisfies an appropriate source condition which includes the second derivative of the cost functional and depends on the geometry of constraints near the solution, we establish accuracy estimates in terms of the error level. Both the a priori and a posteriori parameter choice rules are analyzed.

Imaging quasi‐layered conductive structures by simple processing of transient electromagnetic data

Geophysics ◽  
1987 ◽  
Vol 52 (4) ◽  
pp. 545-554 ◽  
Author(s):  
James Macnae ◽  
Yves Lamontagne
Keyword(s):  
Delay Time ◽  
A Priori ◽  
Step Response ◽  
Layered Earth ◽  
Electromagnetic Data ◽  
Apparent Conductivity ◽  
Data Inversion ◽  
Transient Electromagnetic ◽  
Static Zone ◽  
The Cost

An “imaged” conductivity section of a layered earth can be obtained by simple transformation of step‐response electromagnetic data measured in the quasi‐static zone. This method of data transformation is presented as an alternative to conventional apparent conductivity transformations. At each delay time, the variation of the step response as a function of geometry (transmitter and receiver location) is transformed to an equivalent reference depth h, which can be related to the depth of electromagnetic field diffusion. The behavior of h as a function of delay time is nearly independent of the source‐receiver geometry. The slowness dt/dh divided by the magnetic permeability is almost exactly proportional to the cumulative conductance measured from the surface down to a depth h. Thus we can estimate an apparent conductivity, which we call the “imaged conductivity,” at depth to be [Formula: see text]. The cost of this transformation is a fraction of the cost of conventional data inversion, and it does not require an a priori constraint on the number of parameters used in the inversion. The empirically developed technique was used successfully to process UTEM field data measured over a quasi‐layered earth.

scholarly journals Product Cost Calculation Methods in Construction

2018 ◽  
Vol 7 (3.2) ◽  
pp. 6
Author(s):  
Alla Dmitrenko ◽  
Galyna Lebedyk ◽  
Mykola Nesterenko
Keyword(s):  
Production Cost ◽  
Cost Price ◽  
Cost Calculation ◽  
Operational Control ◽  
Calculation Methods ◽  
Accurate Calculation ◽  
Product Cost ◽  
Practical Activity ◽  
Construction Products ◽  
The Cost

The order of accounting and features of the methodology of cost expenditures at the concrete enterprises of the field was studied and it has been found out the fact that in the practical activity of the enterprise, they tend to apply the normative method of cost expenditures accounting. It has been conducted a detailed research of enterprises which use the normative method of cost expenditure accounting, and the calculation of the planned cost price. In addition, given advantages of the normative method of cost expenditure accounting have two functions: it provides the operational control over the production cost expenditures by accounting for cost expenditures under current norms and their changes and provides accurate calculation of the cost price of construction products. 

scholarly journals EVALUATION OF THE RELIABILITY TEST RESULTS OF A ROCKET ENGINE BASED ON A LOGICAL-PROBABILISTIC METHOD

2019 ◽  
Vol 27 (4) ◽  
pp. 21-24
Author(s):  
Sergey Mikhailovich Podolchak
Keyword(s):  
Rocket Engine ◽  
Probabilistic Method ◽  
A Priori ◽  
Rocket Engines ◽  
Test Results ◽  
Reliability Models ◽  
Complex Technical Systems ◽  
Priori Information ◽  
Theory Of Evidence ◽  
The Cost

A logical-probabilistic method for evaluating the test result is proposed, which is based on the theory of evidence of Dempster-Schafer with some assumptions that do not affect the final result. Currently, there is an acute question of creating new types of rocket technology in connection with a change in the situation on the international and domestic market. When creating new samples, it is necessary to pay special attention to the level of their reliability, but also remember to take into account the financial component of projects for the development and manufacture of products. In this regard, research is currently being conducted not only in the direction of increasing the reliability of complex technical systems, which include rocket engines, but also in reducing the cost of their refinement. One of the research options in this direction was proposed by the author in this work. The aim of the work and research as a whole was to demonstrate the capabilities of the chosen method for evaluating the test results, according to which it would be possible to draw conclusions about the success of the tests themselves. As studies have shown, the logical-probabilistic method for evaluating test results based on the Dempster-Schafer theory of evidence, due to the lack of a priori information, can be used in the development of new rocket engine models, but only in a narrow direction. More widely, this method can be used in the design of products based on accumulated experience (amount of information) on existing analogues. Dempster-Schafer proof theory can be applied at earlier design stages, but only in combination with other reliability models.

scholarly journals Impact of high-resolution <i>a priori</i> profiles on satellite-based formaldehyde retrievals

2017 ◽  
Author(s):  
Si-Wan Kim ◽  
Vijay Natraj ◽  
Seoyoung Lee ◽  
Hyeong-Ahn Kwon ◽  
Rokjin Park ◽  
...  
Keyword(s):  
Los Angeles ◽  
Urban Area ◽  
Temporal Resolution ◽  
A Priori ◽  
Measurement Data ◽  
Tropospheric Chemistry ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Los Angeles Basin ◽  
Model Calculations

Abstract. Formaldehyde (HCHO) is either directly emitted from sources or produced during the oxidation of volatile organic compounds in the troposphere. It is possible to infer atmospheric HCHO concentrations using space-based observations, which may be useful for studying emissions and tropospheric chemistry at urban to global scales depending on the quality of the retrievals. In the near future, an unprecedented volume of satellite-based HCHO measurement data will be available from both geostationary and polar-orbiting platforms. Therefore, it is essential to develop retrieval methods appropriate for the next-generation satellites that measure at higher spatial and temporal resolution than the current ones. In this study, we examine the importance of fine spatial and temporal resolution a priori profile information on the retrieval by conducting approximately 45 000 radiative transfer model calculations in the Los Angeles Basin megacity. Our analyses suggest that an air mass factor (AMF, ratio of slant columns to vertical columns) based on fine spatial and temporal resolution a priori profiles can better capture the spatial distributions of the enhanced HCHO plumes in an urban area than the nearly constant AMFs used for current operational products. For this urban area, the AMF values are inversely proportional to the magnitude of the HCHO mixing ratios in the boundary layer. Using our optimized model HCHO results in the Los Angeles Basin that mimic the HCHO retrievals from future geostationary satellites, we illustrate the effectiveness of HCHO data from geostationary measurements for understanding and predicting tropospheric ozone and its precursors.

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