Even using an authenticated synchronous broadcast model, the task of unforgeably time-stamping digital documents still presents some problems. It is simply not practical to assume that all participants will record and store everyone else's documents so that creation times can be veri ed. This paper presents a time and space e cient method for accumulation of time-stamped documents. Whenever a q...

Papers published in this report series are preliminary versions of journal articles and not for quotations. Abstract This paper extends the real options literature by discussing an investment problem, where a firm has to determine optimal investment timing and optimal capacity choice at the same time under conditions of irreversible investment expenditures and uncertainty in future demand. Afte...

............................................................................................................................. ii Dedication ......................................................................................................................... iii Acknowledgments ............................................................................................................ iv Tab...

Biofilm formation, loose deposit accumulation and water quality deterioration in drinking water distribution systems have been widely reported. However, the accumulation and distribution of harbored elements and microbes in the different niches (loose deposits, PVC-U biofilm, and HDPE biofilm) and their corresponding potential contribution to water quality deterioration remain unknown. This pre...

The paper focuses on bio®lms subject to turbulent ̄ow and high liquid velocity (of the order of 1 m s) which can be found in heat exchangers, water distribution systems and in some wastewater reactors. An overall model describing bio®lm development is presented, which includes the effects of biomass detachment due to the hydrodynamic forces. A methodology for estimating substrate consumption fr...

This review deals with computer simulation of biological aging, particularly with the Penna model of 1995. They are based on the mutation accumulation theory of half a century ago. The results agree well with demographical reality, and also with the seemingly contradictory influence of predators on the aging of prey.

Accumulation of contextual data offers new opportunities to improve the preventative health and wellbeing interventions. In this paper, we discuss the importance of understanding the context elements of Behavior Change Support Systems (BCSSs) and present an Event model illustrating the Use, User and Technology Context factors of the Persuasion Context. The model is a conceptual tool for identif...