scholarly journals Relationships among the Optimal Production Rates, Unit Costs and Profit Rates Determined for Three Economic Criteria

1989 ◽  
Vol 32 (3) ◽  
pp. 310-325 ◽  
Author(s):  
Takayoshi Tamura ◽  
Seiichi Fujita ◽  
Genji Yamazaki
2016 ◽  
Vol 22 (1) ◽  
pp. 35-50 ◽  
Author(s):  
Zied Hajej ◽  
Nidhal Rezg ◽  
Gharbi ali

Purpose – The purpose of this paper is to investigate the optimal production policy and maintenance strategy for leased equipment under a lease contract with warranty periods. In order to have steady revenue, the lessor (owner) of the equipment may provide guaranty periods to encourage the lessee to sign a lease contract with a longer lease period. Design/methodology/approach – Under this production/maintenance scheme, the mathematical model of the expected total cost is developed and the optimal production planning and the corresponding optimal maintenance policy are derived by choosing the optimal warranty periods for the lessee in order to minimize the total cost. Findings – The influence of the production rates variation in the equipment degradation is considered by an increased failure rate according to both time and production rates. The impact of warranty periods on optimal maintenance planning will be studied thereafter. Finally, numerical examples are given to illustrate the analytical study and the effects of the warranty periods variation during the lease periods on the maintenance policy and consequently on the total cost. Originality/value – The paper proposes a new idea of production and maintenance coupling in the leasing aspect. This study shows that it has a novelty and originality relative to this type of problem which considers and proposes a new maintenance strategy for leasing contract. This originality characterized by the influence of two factors on the equipment maintenance strategy. First factor is the influence of the production variation production rates on the machine degradation degree that is new in the literature charactering by analytical equation that shows the evolution of the machine failure rate according to its use (which is in our case the production rate for each period) respecting in the same time the continuity of the equipment reliability for a period to another.


1972 ◽  
Vol 70 (1) ◽  
pp. 89-96 ◽  
Author(s):  
M. J. Levell

ABSTRACT Five normal subjects were given [14C] cortisol in the morning and [3H] cortisol in the evening, in both cases by mouth. The excretion of radioactivity in tetrahydrocortisol (THF) and tetrahydrocortisone (THE) was measured by a modified form of reverse isotope dilution. In 2 subjects, the ratio of isotopic THF/isotopic THE was higher after the evening dose than after the morning dose. In 1 subject the ratio decreased. In 2 subjects it did not change. Cortisol production rates calculated from THF were usually higher than those calculated from THE. The observed variations of metabolism were only a contributory factor to these discrepancies.


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