background : time to donating blood plays a major role in a regular donor to becoming continues one. the aim of this study was to determine the effective factors on the interval between the blood donations. methods : in a longitudinal study in 2008, 864 samples of first-time donors in shahrekord blood transfusion center,  capital city of chaharmahal and bakhtiari province, iran were selected by...

the percent of normal precipitation index (pnpi) is a widely used drought index to provide good estimations about the intensity, magnitude and spatial extent of droughts. the objective of this study was analyzing spatial pattern of drought by pnpi index. in this paper, according to the data of 40 stations in iran, during 1967-2009, the pattern of drought hazard is evaluated. influenced zone of ...

the waiting time between children births are called tempo. this phenomenon plays a crucial role in the child and mother health. the purpose of the present study is determination of factors which influence this variable of interest. a significance level of 5% and power of 80% considered to calculate the required sample size for this cross sectional study. the sample size of 124 women determined ...

objective: tempo is the average waiting time to next birth for a woman. role of fertility as the most important phenomenon determining population fluctuations due to the studies of it compared with other demographic phenomena be important and review the multifarious socioeconomic factors of it share  a large effective population studies. general purpose of this study is fitting the cox model to...

it is essential to use statistical models and theoretical analysis of the data for preparing comprehensive geological and seismic hazard mapping. a cellular automaton consists of an array of cells, each one of which has a finite number of possible states, together with a rule for updating all cells simultaneously based only on the states of neighboring cells. in the present paper, ising cellula...

in many countries, studies to determine the severity of desertification and providing land plans to implement desertification. one of the models is modified medalus or iranian model (imdpa), has been used in present research in order to investigate desertification situation in the tashk region of fars province. in this research, the modified imdpa model used with emphasis on the water, soil and...

background and purpose: the goal of this study is application of the proportional hazards model (ph) and accelerated failure time model (aft), with consideration weibull distribution, to determine the level of effectiveness of the factors affecting on the level of disease-free survival (dfs) of the patients with breast cancer. materials and methods: based on the retrospective descriptive studie...

assessing seismic hazards involves specifying the likelihood, magnitude and location of earthquakes in a region. predicting the seismic hazards is the first step in reducing the impact of the damage caused by an earthquake.  in this study, to fully utilize all the known parameters which may possibly affect the occurrence of earthquakes (mb ≥ 4.5); a data-driven rule-extraction method called the...