Introducing and Evaluating a New Multiple-Component Stochastic Mortality Model
NORTH AMERICAN ACTUARIAL JOURNAL
Authors: Hatzopoulos, Peter; Sagianou, Aliki
Abstract
This work introduces and evaluates a new multiple-component stochastic mortality model. Our proposal is based on a parameter estimation methodology that aims to reveal significant and distinct age clusters by identifying the optimal number of incorporated period and cohort effects. Our methodology adopts sparse principal component analysis and generalized linear models (GLMs), first introduced in Hatzopoulos and Haberman (2011), and it incorporates several novelties. Precisely, our approach is driven by the unexplained variance ratio (UVR) metric to maximize the captured variance of the mortality data and to regulate the sparsity of the model with the aim of acquiring distinct and significant stochastic components. In this way, our model gains a highly informative structure in an efficient way, and it is able to designate an identified mortality trend to a unique age cluster. We also provide an extensive experimental testbed to evaluate the efficiency of the proposed model in terms of fitting and forecasting performance over several datasets (Greece, England and Wales, France, and Japan), and we compare our results to those of well-known mortality models (Lee-Carter, Renshaw-Haberman, Currie, and Plat). Our model is able to achieve high scores over diverse qualitative and quantitative evaluation metrics and outperforms the rest of the models in the majority of the experiments. Our results show the beneficial characteristics of the proposed model and come into agreement with well-established findings in the mortality literature.
Numerical and experimental study of a closed loop for ground heat exchanger coupled with heat pump system and a solar collector for heating a glass greenhouse in north of Tunisia
INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID
Authors: Awani, S.; Kooli, S.; Chargui, R.; Guizani, A.
Abstract
This work emphasizes the exploitation of renewable energy sources for heating a greenhouse, which requires the use of a horizontal heat exchanger, a heat pump associated with a solar collector in numerical and experimental investigations. This study demonstrates the performance of a heat pump system assisted by solar and geothermal energy under the climatic conditions of Tunisia. This system was designed and installed in Thermal Process Laboratory; Research and Technology Centre of Energy CRTEn Borj Cedria. The surface area and of the glass greenhouse used in the experimental model are 14.8 m(2) as surface area. We precede several experimental data for realizing a numerical model based on TRNSYS software. For this point of view a numerical model was improved using 100 m(2) and 229.5 m(3) as surface and volume areas. The water-air heat pump is coupled with a ground heat exchanger (GHE) with 1m of depth. The distance between two consecutive tubes is 0.3 m. The surface area of the solar collector is 8 m(2). (C) 2017 Published by Elsevier Ltd.