Optimizations of Managerial Maintenance Policies

2021 ◽  
Author(s):  
Xiaoning Zhang ◽  
Jiajia Cai ◽  
Xufeng Zhao
Keyword(s):  
Minimal Repair ◽  
Maintenance Costs ◽  
Numerical Examples ◽  
Maintenance Policies ◽  
Two Phases ◽  
Three Phases

This paper takes up managerial maintenance policies during different phases for mission executions. When a mission execution is divided into two phases and three phases respectively, replacement, minimal repair and keeping failure status become alternatives for managerial maintenance policies. Further, we give approximations of the above managerial maintenance policies to make the computations simple. In this paper, keeping failure status is considered as the last choice for the last phase of mission executions. We aim to minimize the expected maintenance costs for the total mission executions. All of the discussions are made analytically and their numerical examples are given.

scholarly journals OPTIMALITY OF CONTROL LIMIT MAINTENANCE POLICIES UNDER NONSTATIONARY DETERIORATION

1999 ◽  
Vol 13 (1) ◽  
pp. 55-70 ◽  
Author(s):  
Zvi Benyamini ◽  
Uri Yechiali
Keyword(s):  
Optimal Policy ◽  
Transition Probabilities ◽  
Stationary Problem ◽  
Control Limit ◽  
Maintenance Costs ◽  
Operation And Maintenance ◽  
Deterioration Process ◽  
Maintenance Policies ◽  
Deteriorating Systems ◽  
Limit Form

Control limit type policies are widely discussed in the literature, particularly regarding the maintenance of deteriorating systems. Previous studies deal mainly with stationary deterioration processes, where costs and transition probabilities depend only on the state of the system, regardless of its cumulative age. In this paper, we consider a nonstationary deterioration process, in which operation and maintenance costs, as well as transition probabilities “deteriorate” with both the system's state and its cumulative age. We discuss conditions under which control limit policies are optimal for such processes and compare them with those used in the analysis of stationary models.Two maintenance models are examined: in the first (as in the majority of classic studies), the only maintenance action allowed is the replacement of the system by a new one. In this case, we show that the nonstationary results are direct generalizations of their counterparts in stationary models. We propose an efficient algorithm for finding the optimal policy, utilizing its control limit form. In the second model we also allow for repairs to better states (without changing the age). In this case, the optimal policy is shown to have the form of a 3-way control limit rule. However, conditions analogous to those used in the stationary problem do not suffice, so additional, more restrictive ones are suggested and discussed.

A COMPREHENSIVE SURVEY OF THE REVIEWER ASSIGNMENT PROBLEM

2010 ◽  
Vol 09 (04) ◽  
pp. 645-668 ◽  
Author(s):  
FAN WANG ◽  
NING SHI ◽  
BEN CHEN
Keyword(s):  
Academic Writing ◽  
Operations Research ◽  
Assignment Problem ◽  
Future Research ◽  
Intelligence Operations ◽  
Comprehensive Survey ◽  
Matching Degree ◽  
Two Phases ◽  
Three Phases

Reviewer Assignment Problem (RAP) is an important issue in peer-review of academic writing. This issue directly influences the quality of the publication and as such is the brickwork of scientific authentication. Due to the obvious limitations of manual assignment, automatic approaches for RAP is in demand. In this paper, we conduct a survey on those automatic approaches appeared in academic literatures. In this paper, regardless of the way reviewer assignment is structured, we formally divide the RAP into three phases: reviewer candidate search, matching degree computation, and assignment optimization. We find that current research mainly focus on one or two phases, but obviously, these three phases are correlative. For each phase, we describe and classify the main issues and methods for addressing them. Methodologies in these three phases have been developed in a variety of research disciplines, including information retrieval, artificial intelligence, operations research, etc. Naturally, we categorize different approaches by these disciplines and provide comments on their advantages and limitations. With an emphasis on identifying the gaps between current approaches and the practical needs, we point out the potential future research opportunities, including integrated optimization, online optimization, etc.

On operation termination for degrading systems with two types of failures

2018 ◽  
Vol 233 (3) ◽  
pp. 419-426 ◽  
Author(s):  
Maxim Finkelstein ◽  
Gregory Levitin ◽  
Oleg A Stepanov
Keyword(s):  
Failure Rate ◽  
Cost Effective ◽  
System Failure ◽  
Minimal Repair ◽  
System Operation ◽  
Numerical Examples ◽  
Relevant Case ◽  
The One ◽  
Combined Strategy

When a failure occurring during a system operation can result in considerable penalties, it can be more cost-effective to terminate the operation at some time avoiding the risk of future failures. This strategy can be relevant for aging systems, for example, when the system failure rate is increasing. The paper analyzes three strategies of termination for systems with major and minor failures. A major failure automatically terminates the operation, whereas the minor failures are minimally repaired. We show that the age-based strategy outperforms the one with termination after the mth minimal repair. The combined strategy when the termination is performed at time t or upon the mth minimal repair, whichever comes first, is also considered. The emphasis for the latter setting is on the practically relevant case when the number of possible minimal repairs is limited. Numerical examples illustrating the findings are presented.

Sociological formation and reception of translation

2019 ◽  
Vol 14 (3) ◽  
pp. 333-350 ◽  
Author(s):  
Minhui Xu ◽  
Jing Yu
Keyword(s):  
Formation Process ◽  
Process Selection ◽  
International Circulation ◽  
Border Town ◽  
Two Phases ◽  
Favorable Conditions ◽  
Three Phases

Abstract This study draws on Bourdieu’s conceptualization of the international circulation of ideas to examine the sociological formation process of a translation. Taking the translated Chinese novel Border Town as an example, this study investigates the three phases of that process: selection; labeling and classification; and reading and reception. It discovers that the first two phases have created favorable conditions for the reception of the translated novel, but the translation was not well received. This article argues that the reception of a translation depends on the success of every phase of the sociological formation process. The reception of a translation is constructed and consecrated through the joint efforts of different agents in each phase. Only through a holistic sociological consideration of the dynamics of the formation process can we reach a real understanding of the reception of a translated work.

scholarly journals Individual Phase Full-Power Testing Method for High-Power STATCOM

Electronics ◽  
2019 ◽  
Vol 8 (7) ◽  
pp. 754 ◽  
Author(s):  
Qingjun Huang ◽  
Bo Li ◽  
Yanjun Tan ◽  
Xinguo Mao ◽  
Siguo Zhu ◽  
...  
Keyword(s):  
High Power ◽  
High Capacity ◽  
Test System ◽  
Testing Method ◽  
Individual Phase ◽  
Test Platform ◽  
Full Power ◽  
Power Testing ◽  
Two Phases ◽  
Three Phases

For a high-power static synchronous compensator (STATCOM), a full-power pre-operation test in the factory is necessary to ensure the product quality of a newly manufactured one. But owing to the hardware limitation and cost of test platform, such test is currently too difficult to conduct in the factory, thus it poses great risk to the on-site operation and commissioning. To address this issue, this paper proposes an individual phase full-power testing method for STATCOM. By changing the port connection, three-phase STATCOM was reconstructed into a structure that two phases are in parallel and then in series with the third-phase, and then connected to two phases of the rated voltage grid. Then by rationally matching the voltage and current of three phases, the parallel phases can get a reactive current hedging under both the rated voltage and rated current, meanwhile three phases maintain their active power balance. As a result, STATCOM gets a phase full-power tested phase by phase. The simulation results in Matlab/Simulink show that, under the proposed test system, both the voltage and current of the parallel two phases get their rated values while the grid current is only about 3% of the rated current, meanwhile the DC-link voltage of each phase converter is stabilized. Compared with other testing methods for STATCOM, this method requires neither extra hardware nor high-capacity power supply to construct the test platform, but it can simultaneously examine both the entire main circuit and a large part of the control system in STATCOM. Therefore, it provides a cost-effective engineering method for the factory test of high-power STATCOM.

The Effect of Lithium Carbonate on the Electroencephalogram of Patients with Affective Disorders

1969 ◽  
Vol 115 (527) ◽  
pp. 1185-1188 ◽  
Author(s):  
S. R. Platman ◽  
R. R. Fieve
Keyword(s):  
Affective Disorders ◽  
Alpha Rhythm ◽  
Lithium Carbonate ◽  
Harmonic Mean ◽  
Common Pattern ◽  
Manic Depressive ◽  
Two Phases ◽  
Depressive Patients ◽  
Three Phases

This paper examines the degree of electroencephalogram abnormality among the three phases of manic-depressive disease and the changes brought about by lithium carbonate. The earlier investigators (Berger, 1931; Lemere, 1936) reported no abnormalities in the EEGs of manic-depressive patients. Later workers (Davis, 1941; Hurst et al., 1954; Hes, 1960) found prominent changes between the two phases. However, Harding et al. (1966) noted no common pattern in their three cases when analysed for mean abundance, harmonic mean and variability of alpha rhythm.

OPTIMAL PREVENTIVE-MAINTENANCE WARRANTY POLICIES FOR REPAIRABLE PRODUCTS WITH AGE-DEPENDENT MAINTENANCE COSTS

2005 ◽  
Vol 12 (02) ◽  
pp. 111-125 ◽  
Author(s):  
RUEY HUEI YEH ◽  
MING-YUH CHEN
Keyword(s):  
Optimal Policy ◽  
Preventive Maintenance ◽  
Life Time ◽  
Optimal Number ◽  
Closed Form Expression ◽  
Minimal Repair ◽  
Maintenance Costs ◽  
Special Cases ◽  
Age Dependent ◽  
The Impact

This paper develops a mathematical model to derive the optimal preventive maintenance warranty (PMW) policy for repairable products with age-dependent maintenance costs. Under a PMW, any product failures are rectified by minimal repair, and additional preventive maintenance actions are carried out within the warranty period. When the costs for preventive maintenance and minimal repair are age-dependent, the optimal number of preventive maintenance actions, corresponding maintenance degrees, and the maintenance schedule for designing a PMW policy are derived here such that the expected total warranty cost is minimized. Under some reasonable conditions, we show that there exists a unique optimal PMW policy in which the product is maintained periodically with the same preventive maintenance degree. Using this property, an efficient algorithm is provided to search for the optimal policy. Some related models developed in the literature are discussed and these models are in fact special cases of the model proposed in this paper. Furthermore, when the life-time distribution of a product is Weibull, a closed-form expression of the optimal policy is obtained. Finally, the impact of providing preventive maintenance is evaluated through numerical examples.

The Later Prehistory of Malta

1961 ◽  
Vol 27 ◽  
pp. 253-262 ◽  
Author(s):  
D. H. Trump
Keyword(s):  
Bronze Age ◽  
Single Site ◽  
Urgent Problem ◽  
First Millennium ◽  
The Absolute ◽  
Two Phases ◽  
Sketch Plan ◽  
Small Finds ◽  
Three Phases

For many years down to 1953, our knowledge of Maltese prehistory could be summed up succinctly if rather unkindly in the phrase—‘Neolithic 3,000 B.C., Bronze Age 2,000, Punic 1,000.’ In that year, J. D. Evans's researches were published in these Proceedings. These at last provided a framework for his Period I, no longer called ‘Neolithic’ because the overlap of its later phases with metal-using cultures in nearby Sicily made it unlikely that metal was quite unknown. It was assigned a duration from the mid-second to mid-first millennium B.C. The absolute chronology will need revision in the light of the C-14 dates not then available and the correlations with the Sicilian development have met with some criticism. In any case, the isolation of the different phases was an enormous advance on which all further work in Malta will have to be based, even if, as at the time of writing begins to seem likely, certain amendments to the sequence become necessary. The later prehistoric Period II, lasting down to the 9th century when the Phoenician settlement opened Period III, was described in much less detail.Enormous quantities of material of the first period, megalithic buildings as well as pottery and small finds, were available for study: the material remains of Period II were much more scanty, there being in effect at that time only a single site known of each of its three phases, which were correspondingly named after the Tarxien Cemetery, Borġ in-Nadur and Baħrija. In 1956, Evans published a more detailed study of the first of these phases bringing forward evidence for attributing to it the local dolmens. Phases II B and C were not ready for such treatment as the only excavations were at Borġ in-Nadur in 1881 (a sketch plan found in a Valletta photographer's shop twenty years later being the only record) and 1921-7 (disturbed levels overlying a Period I temple); and at Baħrija in 1909 (three days' work). These two phases therefore remained the most urgent problem in the prehistory of Malta. Accordingly, further excavation was undertaken on their type sites by the Museum Department of the Maltese Government in the spring and autumn of 1959.

scholarly journals First Results and Perspectives of a New Archaeological Project in the Armenian Capital Artaxata: From Artashes-Artaxias I to Roman Imperialism

Electrum ◽  
2021 ◽  
Vol 28 ◽  
pp. 245-276
Author(s):  
Achim Lichtenberger ◽  
Torben Schreiber ◽  
Mkrtich H. Zardaryan
Keyword(s):  
The South ◽  
Roman Imperialism ◽  
The North ◽  
Exact Function ◽  
First Results ◽  
Archaeological Project ◽  
Two Phases ◽  
Roman Province ◽  
The City ◽  
Three Phases

The paper deals with the first results of the Armenian-German Artaxata Project which was initiated in 2018. The city of Artaxata was founded in the 2nd century BC as the capital of the Artaxiad kingdom. The city stretches over the 13 hills of the Khor Virap heights and the adjacent plain in the Ararat valley. The new project focusses on Hill XIII and the Lower city to the south and the north of it. This area was investigated by magnetic prospections in 2018 and on the basis of its results, in total eleven 5 × 5 m trenches were excavated in 2019. On the eastern part of Hill XIII several structures of possibly domestic function were uncovered. They were laid out according to a regular plan and in total three phases could be determined. According to 14C data, the first phase already dates to the 2nd century BC while the subsequent two phases continue into the 1st/2nd century AD. In the 2019 campaign, the overall layout and exact function of the structures could not be determined and more excavations will be undertaken in the forthcoming years. North of Hill XIII the foundations of piers of an unfinished Roman aqueduct on arches were excavated. This aqueduct is attributed to the period 114–117 AD when Rome in vain tried to establish the Roman province of Armenia with Artaxata being the capital.

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