scholarly journals Features of Forecasting Reliability of 6—10 kV Overhead Electric Lines According to Statistics of Their Failures and Reconditionings

Author(s):  
Vladislav Basmanov ◽  
◽  
Valerii Kholmanskikh ◽  

This work is aimed at forecasting justification of the failure time of the 6—10 kV overhead electric lines (OEL) during the normalized period in its operation based on comparison with the statistics of failures and reconditionings on the previous intervals with the use of the OEL availability function, statistical availability coefficient, normalized forecasting interval and the accepted values of the availability coefficient on the forecasting interval. To achieve the goal set the OEL is described as an object of a multiple action, its failure and reconditioning flows are accepted as the simplest Poisson, and for the theoretical analysis of the variation character in the availability coefficient, the probability theory methods along with a mass service were used. The most significant result is justification of the use for the forecasting of the OEL failure time of a new convenient exponential expression of its availability function on the normalized period of time being forecasted. Unlike the accepted in the theory of reliability the availability function with two parameters T and Tr.av (average times of work and reconditionings), the proposed expression uses one parameter of distribution (virtual non-failure operating time). The significance of the results obtained consists in that controlling the dynamics of the variation in the statistical coefficient of availability of the OEL on the previous time intervals makes it possible to forecast its failure time during the forthcoming normalized periods of operation.

2001 ◽  
Vol 33 (1) ◽  
pp. 206-222 ◽  
Author(s):  
Xiaoyue Jiang ◽  
Viliam Makis ◽  
Andrew K. S. Jardine

In this paper, we study a maintenance model with general repair and two types of replacement: failure and preventive replacement. When the system fails a decision is made whether to replace or repair it. The repair degree that affects the virtual age of the system is assumed to be a random function of the repair-cost and the virtual age at failure time. The system can be preventively replaced at any time before failure. The objective is to find the repair/replacement policy minimizing the long-run expected average cost per unit time. It is shown that a generalized repair-cost-limit policy is optimal and the preventive replacement time depends on the virtual age of the system and on the length of the operating time since the last repair. Computational procedures for finding the optimal repair-cost limit and the optimal average cost are developed. This model includes many well-known models as special cases and the approach provides a unified treatment of a wide class of maintenance models.


Author(s):  
Ю.В. Горгуца

При проектировании рейдовых причалов, строительство которых получило широкое развитие в настоящее время, невозможно воспользоваться методами, предлагаемыми ныне действующими Нормами технологического проектирования, так как они были выполнены для традиционных защищённых акваторий и опираются на статистический материал, полученный по существующим портам. Для разработки методов определения простоев судов при обработке судов на рейдовых причалах с учётом потока помех от метеофакторов (штормов) как потока случайных событий в данной статье описывается исследование новых моделей систем массового обслуживания. Используется метод суперпозиций – находятся решения для простых моделей, которые затем используются для получения решений по более сложным моделям. Первоначально рассматривается простейшая модель, состоящая из потоков вызовов (штормов) и прибора (порта). Поток вызовов - пуассоновский. Время обслуживания – произвольное с преобразованием Лапласа-Стилтьеса Полученные результаты используются для исследования модели с потоками помех от ветров двух различных направлений. Далее исследуется однолинейная модель с «ненадёжным» прибором. Входящий поток – пуассоновский поток подходящих к порту судов. Время обслуживания - длительность интервалов времени между освобождением места у причала для судна, ожидающих на рейде. Выход из строя прибора, как в свободном, так и в занятом обслуживанием состоянии определяется наступлением шторма – событием пуассоновского потока с интервалами между событиями – интервалами между наступлением штормов. Длительность восстановления работоспособности прибора – определяемая в первой модели длительность простоя причала из-за воздействия метеофакторов. Суда, оказавшиеся в порту при наступлении шторма «дообслуживаются» после его окончания Итоговая модель – многоканальная с параллельно работающими приборами (причалам) и экспоненциальным временем обслуживания судов. Полученные результаты сравнивались со статистическими и показали их высокую сходимость, что доказывает их достоверность. While designing offshore terminals, which are being built quite widely in recent time, it is impossible to use methods, proposed by current technological design norms, because they were created for traditional protected waters and are based on statistical data, acquired by existing ports. This article describes the research of new models of mass service systems to develop methods of defining demurrage while processing vehicles on offshore terminals, taking into account disturbance flow from weather factors (storms) as flow of random events. Method of superpositions is used - to find solutions for simple models, which are used afterwards for getting solutions for more complicated models. Initially the basic model is reviewed, consisting of flow of challenges (storms) and device (port). Challenges flow is Poisson. Service time - arbitrary with transformation of Laplace-Stiltjes. Results acquired are used for researching the model with disturbance flows from windows of various directions. Next the unilineal model with “unreliable” device is researched. Incoming flow is Poisson flow of incoming vehicles. Service time - length of time intervals between berths exemption for vehicles awaing on raid. Device failure, both in free and in maintenance mode was defined by storm incoming - the event of Poisson flow with intervals between events - intervals between storms. Duration of device efficiency recovery - is the defined in the first model duration of terminal demurrage due to weather influence. Vessels, caught up in the port during storm will be maintained after its end. Final model is multi-channel one with working devices (terminals) and exponential time of vessel service. Acquired results have been compared with statistical data, which showed they high convergence, proving their reliability.


Circulation ◽  
2020 ◽  
Vol 142 (Suppl_4) ◽  
Author(s):  
Mengqi Gao ◽  
Chenguang Liu ◽  
Dawn Jorgenson

Background: Early defibrillation with an automated external defibrillator (AED) is crucial for improving the survival rate in out-of-hospital resuscitation from sudden cardiac arrest (SCA). Chance of survival decreases by 7% to 10% for every minute that defibrillation is delayed. While simulation studies have been used to assess AED usability factors, our objective was to report the actual operating time for three Philips AED models used in SCA responses. Methods: A convenience dataset recorded by Philips AEDs (HS1, FRx, or FR3) was obtained from Europe and the United States from 2007 - 2018. The HS1 is intended for minimally trained or untrained individuals, the FRx is for Basic Life Support (BLS), and the FR3 is for both BLS and Advanced Life Support (ALS) responders. A retrospective analysis was conducted to report the operating time intervals for cases where a shock was delivered after initial rhythm analysis. The study analyzed 90 HS1, 46 FRx and 32 FR3 cases. Results: Compared with HS1, both FRx (p < 0.001) and FR3 (p = 0.001) responders spent less time in placing pads on the patient after powering on the AED (Figure 1) as expected. Similarly, time intervals from the start of shock advised prompt to first shock delivery for FRx (p = 0.02) and FR3 (p < 0.01) are shorter than for HS1. Time from AED power-on to first shock was within 90 seconds in 74.4% (67 of 90) HS1 cases, 97.8% (45 of 46) FRx cases, and 100% (32 of 32) FR3 cases. On average, the FR3 and FRx responders were able to deliver the first shock within 48 seconds. Conclusions: The analysis shows that responders were able to quickly apply the AEDs and respond to the shock advisory prompt for all three AED models despite different training levels. This real-world performance is better than most reported simulation studies, however, this analysis cannot convey variety of activities that account for the differences in timing (e.g. pads applied before power-on, or compressions began before applying pads, etc.).


1970 ◽  
Vol 2 (02) ◽  
pp. 287-322
Author(s):  
T. Gergely ◽  
I. N. Tsukanow ◽  
I. I. Yezhow

In this work Markov chains governed by complicated processes are introduced and investigated (Section 1). In Section 2 an ergodic theorem for these processes is formulated, while in Section 3 the sojourn time of the process in a fixed region is studied; in Section 4 some examples are considered. The processes studied are of practical importance in the description of mass service systems and the theory of reliability for which the time intervals between successive demands cannot be assumed to be mutually independent random variables. It is shown that the dependence parameter r of these processes, if it is sufficiently large, allows us to formulate a relationship between the time intervals in question.


2017 ◽  
Vol 2017 (4) ◽  
pp. 290-307 ◽  
Author(s):  
Fatemeh Rezaei ◽  
Amir Houmansadr

Abstract Flow fingerprinting is a mechanism for linking obfuscated network flows at large scale. In this paper, we introduce the first blind flow fingerprinting system called TagIt. Our system works by modulating fingerprint signals into the timing patterns of network flows through slightly delaying packets into secret time intervals only known to the fingerprinting parties. We design TagIt to to enable reliable fingerprint extraction by legitimate fingerprinting parties despite natural network noise, but invisible to an adversary who does not possess the secret fingerprinting key. TagIt makes use of randomization to resist various detection attacks such as multi-flow attacks. We evaluate the performance and invisibility of TagIt through theoretical analysis as well as simulations and experimentation on live network flows.


2019 ◽  
Vol 10 (1) ◽  
pp. 76-84
Author(s):  
Hamid Hamli Benzahar

PurposeThe purpose of this paper is to evaluate theoretically and numerically the stress and stress intensity factor (SIF) at the time of propagation of the crack in bi-material. The problem is formulated using two thin materials which are bound by a cracked adhesive at the tip and having a micro-crack in one of these two materials.Design/methodology/approachThe plane stresses and the SIF will be determined as a function of two parameters (Poisson’s ratio and Shear modulus). The numerical analysis is carried out on a flat element, having a main crack in one of these ends, and a micro-crack varies in the vicinity of this main crack. The problem is analyzed by the finite element method and processed by computational software (ABAQUS).FindingsThe numerical and theoretical analysis allowed the author to determine and compare the values of plane stresses and SIF in each area of the material.Originality/valueThe theoretical analysis of SIF is based mainly on a mathematical calculation of equations of plane stresses; these equations are determined by development of complex analytical functions of bi-materials given by other researchers. Using the numerical method, several models are modeled by changing the micro-crack position relative to the main crack to determine the plane stresses and SIF for each position.


2015 ◽  
Vol 2 ◽  
pp. 3-13
Author(s):  
Christopher Hickin ◽  
Henry Li ◽  
Sharnan Kemp

In the development of renewable energy sources, there has been a trend toward increasing and stabilising the power output of Concentrated Solar Power Plants (CSPPs) during times of reduced solar resource through the use of Thermal Energy Storage Devices (TESDs). This study investigates whether the use of a molten salt TESD decreases the efficiency of a parabolic trough CSPP due to additional system energy losses despite prolonging the operational time of the CSPP. A theoretical analysis of a simplified CSPP was made to determine if a TESD would impact the efficiency of the CSPP. This was followed up by a survey of currently active parabolic trough CSPPs both with and without molten salt TESDs. The theoretical analysis illustrated that a TESD would have no effect on the efficiency of a CSPP. However, the survey revealed that the use of a TESD improved the efficiency of a CSPP. The results of the study don't support the theoretical analysis or the hypothesis suggesting that a property has been overlooked. This property is most likely to be that generators tend to operate best within a certain temperature range, and in a CSPP the optimum temperature range cannot be maintained. This results in a generator being selected capable of operating for the longest period with the lowest amount of excess solar energy. When a TESD is implemented, the excess solar energy is stored for later use, prolonging the generator's running time and increasing the useable energy. The realisation of the ability of a TESD to increase the efficiency of a CSPP as well as extending its operating time shows a promising area of development in CSPP technology and increasing its application in electricity generation.


1970 ◽  
Vol 2 (2) ◽  
pp. 287-322 ◽  
Author(s):  
T. Gergely ◽  
I. N. Tsukanow ◽  
I. I. Yezhow

In this work Markov chains governed by complicated processes are introduced and investigated (Section 1). In Section 2 an ergodic theorem for these processes is formulated, while in Section 3 the sojourn time of the process in a fixed region is studied; in Section 4 some examples are considered. The processes studied are of practical importance in the description of mass service systems and the theory of reliability for which the time intervals between successive demands cannot be assumed to be mutually independent random variables. It is shown that the dependence parameter r of these processes, if it is sufficiently large, allows us to formulate a relationship between the time intervals in question.


2011 ◽  
Vol 268-270 ◽  
pp. 1484-1487
Author(s):  
Zhi Bin Yu ◽  
Chun Xia Chen

The one-dimensional feature-separability model concerning the feature-separability issue of radar emitter signals is proposed based on the probability theory and statistical theory, to evaluate the deinterleaving and recognition capability of extracted features. The proposed method is applied to analyze convention features of radar emitter signals. The theoretical analysis and experimental results show that the proposed model offers a new way to analyze the validity of extracted features, and is valid in both the original feature space and linear-transformed feature space.


2021 ◽  
Vol 42 (3) ◽  
Author(s):  
Maxim Piskunov

In the practice of using cut-to-length technology, hydraulic manipulators are widely used. Understanding manipulator cycle is important for improving existing logging technologies and developing new machine designs. The paper analyzes structure of technological cycle and operating time of manipulator in the process of loading forwarder on skid trails. Twenty-one loading processes were investigated. In the structure of technological cycle, the following elements were considered: empty movements, loaded movements, movements of manipulator links when performing operations inside load space of forwarder and special techniques such as re-grabbing logs and pulling of an incompletely closed log grip through the logs when the ends of the grabbed logs tilt and abut against the ground used during loading movement. Statistical processing of data showed that median values of samples consisting of time intervals of empty movements are in trange from 3.8 to 6 seconds, the median of samples of loaded movements is 6–16 seconds and median of samples of a pair of movements 5–9 seconds. With a 95% degree of probability, under the studied production conditions, the time of one loaded movement falls within the range of 4–14 seconds; one empty movement – in the range of 3–7 seconds. Total time of empty movements takes a share from 20 to 45% of the total loading time (on average 30%), the total time of loading movements is from 51 to 72% (on average 63%), the time of operations inside the load space is from 0 to 18% (on average 7%). Time of loaded movements, including use of special techniques, is from 13% to 64% of total time of loaded movements (or 10–53% of total number of loaded movements). The time, consisting of a pair of movements: empty and loaded, is somewhat influenced by forwarder size. Duration of one loaded movement is significantly affected by use of special techniques by the operator. Number and duration of loaded movements with these techniques is significantly influenced by: average size of loaded assortments and number of assortments carried in the grapple during one loaded movement. No significant influence of average size of assortments, number of assortments in grapple and size of the machine on empty movements was found. However, some influence on empty movements of number of loaded movements performed from one forwarder parking lot was observed. Duration and frequency of operations within the load space are weakly correlated with the size of assortments and forwarder size.


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