Armin Lawi

Inventory model of supply chain management 3-echelon multi-tiers

The SCM model of 3-echelon is used to optimize the expenditure by minimizing the inventory use that can generally increase the additional expenditure in the system. This paper develops an SCM model of 3-echelon multi-tiers that is comprised suppliers s, producers p, and retails r. The model was developed using deterioration rate assumption of raw material and finished product following Weibull distribution rate. The research use Taylors expansion method to determine the numeric solution of the model that had been developed. The result indicates that the developed model can be used to optimize the total expenditure in the system of SCM 3-echelon multi-tiers.

Estimating piecewise exponential frailty model with changing prior for baseline hazard function

Piecewise exponential models provide a very flexible framework for modelling univariate survival data. It can be used to estimate the effects of different covariates which are influenced by the survival data. Although in a strict sense it is a parametric model, a piecewise exponential hazard can approximate any shape of a parametric baseline hazard. In the parametric baseline hazard, the hazard function for each individual may depend on a set of risk factors or explanatory variables. However, it usually does not explain all such variables which are known or measurable, and these variables become interesting to be considered. This unknown and unobservable risk factor of the hazard function is often termed as the individual’s heterogeneity or frailty. This paper analyses the effects of unobserved population heterogeneity in patients’ survival times. The issue of model choice through variable selection is also considered. A sensitivity analysis is conducted to assess the influence of the prior for each param...