Time constants for moisture diffusion through a permeable barrier into an airspace

This paper arose from a study of the use of polymeric materials to protect humidity-sensitive items from damp ambient conditions. A one-dimensional model for the Fickian diffusion of moisture through a permeable wall into a volume of air is considered. The humidity in the airspace asymptotically approaches equilibrium with the exterior, and the time constant is defined as the time to reach 1–1/e of its ultimate value. Exact and approximate solutions are considered. Depending on the system geometry and properties, the time constant is either permeability-controlled or diffusivity-controlled, or somewhere in between. Under certain conditions, there exists an optimum combination of airspace depth and wall thickness that maximizes the time constant.     

Provisioning services on digital switching systems

The overall service provisioning process is functionally decomposed into three phases. The first is service negotiation, in which the customer's request is translated into machine-readable form (as a service order). The service order is the input to the second phase, assignment. If network resources are needed to satisfy the service request, the assignment process selects then from its inventory. The third phase is service activation. Attention is focused on the assignment phase, but emerging relationships among the three phases are also covered. The discussion begins with progress to date. Capabilities that have recently become available in Bellcore's operations systems using the flexible entity approach, are described. Issues and problems that arise as the switched network evolves to a greater degree of intelligence are considered, covering provisioning for ISDN, load balancing, service negotiation and assignment, customers doing their own provisioning, and physical and logical provisioning