Background: Premature ovarian failure (POF) is defined by the association of amenorrhea, hypoestrogenism and elevated (menopausal) levels of serum gonadotropins before age of 40 years-old. This condition affects approximately %1 of women under 40 years of age. Physiologic replacement of ovarian steroid hormones seems rational until the age of normal menopause. Temporary return of ovarian functi...

In many situations, it may be more economical to use a used unit than to do a new one. This paper considers an age replacement policy and a periodic replacement policy with minimal repair at failure for a used unit of age x. We discuss optimum replacement policies which minimize the expected cost rates for a specified age x. Further, we obtain an upper bound of an optimum time for an age replac...

background: premature ovarian failure (pof) is a common condition; its incidence is estimated to be as great as 1 in 100 by the age of 40 years. physiologic replacement of ovarian steroid hormones seems rational until the age of normal menopause. temporary return of ovarian function and pregnancy may occur rarely in women with pof. we report a case of pof who conceived during hormone replacemen...

Age replacement policy is concerned with finding an optional time to minimize the cost, at which time the unit is replaced even if it does not fail. So far, age replacement policy involving random age has been proposed. This paper will assume the age of the unit is an uncertain variable, and find the optimal time to replace the unit.

We consider opportunity-based age replacement using nonparametric predictive inference (NPI) for the time to failure of a future unit. Based on n observed failure times, NPI provides lower and upper bounds for the survival function for the time to failure Xn+1 of a future unit, which lead to upper and lower cost functions, respectively, for opportunitybased age replacement based on the renewal ...

The early age shrinkage is responsible for the early age cracking of concrete. It is very critical for durability of concrete. The change in volume of concrete due to evaporation of water or dehydration process is known as shrinkage. To reduce the early age shrinkage utilized the supplementary cementitious material (SCM) in concrete. In present research industrial and agricultural waste byprodu...

An age replacement maintenance policy is considered here, in which a system is restored whenever it fails, or ages without failure up to a preventive maintenance epoch (whichever comes first). The duration of the restoration activity is random, and depends on whether it was precipitated by a failure or by a preventive maintenance action. The case where the preventive maintenance epoch is determ...

In this article, two different systems subject to shocks occurring based on a non-homogeneous Poisson process (NHPP) are analyzed. Type –I system is consisted of a single unit and type –II system is consisted of two parallel units in which both units operate identically and simultaneously. In type –I system occurrence of a shock causes system stopping and consequently will be received minimal r...

from may 1994 to december 1996 thirty patients received viable fresh aortic homografts. mean age was 55 years (13 to 70), male to female ratio was 2/1, 24 operations were elective whereas 6 were semiurgent. predominant lesions were aortic stenosis or regurgitation in lb patients, aortic valve endocarditis in 10, prosthetic valve dysfunction in 3, and aortic root pathology in one patient. from t...