Abstract: The present invention provides the ability to use an existing store-and-forward messaging network such as an electronic mail system to replicate data between computer sites. The replication provided by the present invention can be used with software applications, such as workgroup applications, to replicate data located on multiple sites. Workgroup replication data is sent to other sites via electronic mail ("e-mail") messages. The present invention provides reliability features to handle errors in electronic mail transmissions. For example, the present invention provides the ability to reassemble objects at a replication site such that an object and all of its dependencies exist prior to the object's use at the site. Messages referred to as "ACK" messages are used to communicate a site's state and to provide other control information. Each site maintains latency information to determine transmission failures.

Abstract: The flow of air into a catalyst regenerator is automatically controlled by controlling a side air stream responsive to a computed desired total air flow signal and by controlling a main air stream at a constant value. This constant value is changed if two conditions simultaneously occur: The time elapsed since the last change of said constant value is not shorter than a given minimal value, and the control of the side air stream exceeds the limit of the side air controller.

Abstract: Control of a fractionation column is accomplished by manipulating the flow rate of the external reflux in response to a calculation of the internal reflux flow rate to maintain the actual flow rate of the internal reflux at a substantially constant, desired value. An improved method for calculating the internal reflux flow rate when the heats of vaporization of the external and internal reflux are different utilizes a constant, representative of the heat of vaporization of the external reflux divided by the heat of vaporization of the internal reflux, to obtain an accurate calculation of the internal reflux flow rate. Greater accuracy in the calculation yields improved control of the fractionation column. Alternatively, the constant, representative of the heat of vaporization of the external reflux divided by the heat of vaporization of the internal reflux, may be utilized to calculate the required flow rate of the external reflux necessary to maintain some desired internal reflux flow rate.

Abstract: From the values for the recycle oil feed rate and the fresh oil feed rate of a hydrocracker a material balance conversion computation is carried out resulting in a material balance conversion signal. From the values for the hydrogen flow rate the temperatures and the pressures thereof and the total oil feed flow rate and the flow rate and temperature of the material leaving the hydrocracker, an enthalpy balance conversion computation is carried out resulting in an enthalpy balance conversion signal. The material balance conversion signal and the enthalpy balance conversion signals are computed into a control signal. The control signal regulates the temperature of the total charge to the hydrocracker to maintain the actual percentage conversion at a desired value.