Abstract: A system and method for enabling firewalled access to a client object residing behind a firewall, via an exported callback reference, by a server object outside the firewall. The system includes callback registry accessible by a proxy operating in conjunction with the firewall. The callback registry proxifies the callback object reference so that a callback will be directed to the proxy which in turn will redirect the callback to the callback object. Callback registry, additionally, stores callback definitions, callback registration and access control policies associated with registered callback objects. These access policies are applied to the callback for the server object to ensure that only authorized objects make the callback on authorized callback objects and their operations.

Abstract: A method of determining the rate of heat transfer from a surface due to fluid convection, in which a sheet of liquid absorbent material, whose transmissive or reflective properties for certain radiations vary with the liquid content, is attached to the surface and, after being wetted with a liquid which will evaporate on passage of the convective fluid, the sheet is exposed to the radiation and to the convecting fluid, and the change in the amount of radiation transmitted through or reflected from the sheet is monitored, this giving a ready indication of the rate of heat transfer.