A theoretical explanation is given for the observed difference between the frequency at which the peak of the spectrum of a train of short, locked magnetron pulses occurs and the frequency of the CW ...locking signal.
Three samples of college students received questionnaires regarding their sexual philosophies, behaviour, relationship with most recent partner, self-perceived attractiveness, relationship with ...parents, use of drugs and alcohol, attitudes toward marriage and abortion, and other subjects. The college was sampled in 1974, 1979, and 1986. (Abstract amended)
Air content in the condensing zone can be reduced by several techniques. The best one is keeping the steam shower close to the sheet, thereby mechanically doctoring off much of the air film following ...the sheet. Keeping the steam shower close to the sheet has the additional advantage of reducing steam spillage. High-velocity steam can also be used to penetrate through the air layer to the condensing surface. Another technique is to draw the air through the sheet with a vacuum and still another method is to doctor off the air film with a high-velocity steam curtain located at the leading edge of the steam shower. To satisfy the above requirements, there must exist a means to monitor the steam temperature at the point of application, and a unit to control and adjust the supply steam temperature and pressure. For steam temperature measurement two thermal wells should be provided in the final discharge chamber of the steam box to house temperature sensors. The temperature-measurement signal can be used for simple display and manual adjustment of the steam preparation unit or for remote automatic control. Figure 12 shows a conceptual layout of supervisory control for a steam-conditioning unit. Abstract: Increasing wet end sheet temperature using steam showers or other sources of heat, has long proven effective in improving water removal in the forming and pressing sections. Increasing sheet temperature assists in mechanical water removal by lowering water viscosity and reducing water surface tension. Steam showers have been successfully used at the wet end for many years for profile control, to increase machine speed and to enhance paper properties. In recent years, a number of improvements in their design have resulted in increased performance and improved maintainability of the equipment. This paper considers the trends to smaller zone sizes for improved cross-direction (CD) moisture profile control. In addition, the use of in-situ thermowells for optimizing steam temperature and resulting steambox performance is discussed. The use of removable screen plates for enhanced maintainability is reviewed as is the use of wet end scanners for control. The benefits of using multiple steam boxes are also reviewed.
External induction heating on hard nip for CD caliper control--Board grades: Figure 9 shows a Calcoil induction heating system for CD caliper control applied to a single-nip pre-coater calender stack ...on a multi-ply board machine operating in the 200 to 300 m/min range. The application of CD induction energy on the solid roll is very effective in controlling the CD caliper profile and, in addition, produces an increase in roll surface temperature from an average of 70DegreeC to 170DegreeC or greater. The temperature is controlled by adjusting the base-load of the caliper control system. External induction heating on soft nips for CD caliper control and mass heating--Groundwood: The need for a powerful actuator for CD caliper control and mass roll heating on soft-nip calenders is well known. Figure 12 shows a typical soft-nip calender with an induction heating system installed. The goal of this installation is ultimately to provide both CD profile control and base-load heating (as discussed in Fig. 3a). At the moment, the system is operating at 1000 m/min and roll surface temperature of 115DegreeC. External induction heating on soft nips for mass heating plus CD temperature control--Pilot calender: Figure 14 shows the application of induction heating on a pilot calender. In this instance the induction heating provides the total energy input to the solid roll in excess of 150 kW/m. The application also allows operation at temperatures of 250DegreeC and machine speeds of over 1000 m/min. The CD temperature profile on the roll is adjusted using the Calcoil.
