Methods for preform and tube draw based on controlling forming zone viscosity determined by calculating a holding force exerted by the glass component in the forming zone on the strand being drawn below. The holding force may be calculated by determining a gravitational force applied to the strand and a pulling force applied to the strand by a pulling device, where the holding force is equal to the opposite of the algebraic sum of the gravitational and pulling forces. The holding force may also be calculated by measuring a stress-induced birefringence in the strand at a point between the forming zone and the pulling device, determining an amount of force applied to the strand at the point corresponding to the birefringence, and calculating the holding force by correcting the amount of force for a gravitational effect of the weight of the strand between the forming zone and the point.

Methods for preform and tube draw based on controlling forming zone viscosity determined by calculating a holding force exerted by the glass component in the forming zone on the strand being drawn below. The holding force may be calculated by determining a gravitational force applied to the strand and a pulling force applied to the strand by a pulling device, where the holding force is equal to the opposite of the algebraic sum of the gravitational and pulling forces. The holding force may also be calculated by measuring a stress-induced birefringence in the strand at a point between the forming zone and the pulling device, determining an amount of force applied to the strand at the point corresponding to the birefringence, and calculating the holding force by correcting the amount of force for a gravitational effect of the weight of the strand between the forming zone and the point.

A method for determining a mass flow of ammonia between two SCR catalytic converters disposed one after the other in an SCR catalytic converter system in an exhaust system, which comprises only one reduction agent dosing unit upstream of the first SCR catalytic converter, characterized in that the determination is carried out from the signal of a NOx sensor disposed between the two SCR catalytic converters and the signal of a NOx sensor disposed downstream of the second SCR catalytic converter.

A method for determining a mass flow of ammonia between two SCR catalytic converters disposed one after the other in an SCR catalytic converter system in an exhaust system, which comprises only one reduction agent dosing unit upstream of the first SCR catalytic converter, characterized in that the determination is carried out from the signal of a NOx sensor disposed between the two SCR catalytic converters and the signal of a NOx sensor disposed downstream of the second SCR catalytic converter.

Evaluating surfactants for use in downhole applications, especially surfactants with similar surface tension or interfacial tension values and wetting properties, may be achieved with a sensitive column test using a non-uniform particulate media therein. An exemplary method may include providing a column containing two types of particles that differ by at least one of: a mean particle diameter, a sphericity, and a chemical composition. Surfactant samples may be individually tested by passing the sample through the column followed by a displacement fluid, typically an oleaginous. The displacement rate and volume of the surfactant sample may be used to assess the surfactant's suitability for downhole applications.

Methods and systems for determining slip velocity of drill cuttings obtained from subsurface formations are disclosed. The system includes a first cylindrical tube having a first diameter and a first length, wherein the first tube is attached to a base plate, a second cylindrical tube having a second dimeter smaller than the first diameter and a second length larger than the first length, the second tube attached to a lower portion of the first tube and running substantially parallel to the first tube, and an ultrasonic device operatively connected to an opening of the second tube for measuring a level of a fluid in the second tube, and a computer operatively connected to the ultrasonic device, the computer configured to store and analyze data received from the ultrasonic device.

Methods and systems for determining slip velocity of drill cuttings obtained from subsurface formations are disclosed. The system includes a first cylindrical tube having a first diameter and a first length, wherein the first tube is attached to a base plate, a second cylindrical tube having a second dimeter smaller than the first diameter and a second length larger than the first length, the second tube attached to a lower portion of the first tube and running substantially parallel to the first tube, and an ultrasonic device operatively connected to an opening of the second tube for measuring a level of a fluid in the second tube, and a computer operatively connected to the ultrasonic device, the computer configured to store and analyze data received from the ultrasonic device.

A capillary bridge viscometer, comprises an input port (flow in) an output port (flow out) a first capillary tubing arm (R1) in a first hydraulic path between the input port and a first differential detection point (DP+), a second capillary tubing arm (R3) in a second hydraulic path between the first differential detection point (DP+) and the output port (flow out), a third capillary tubing arm (R2) in a third hydraulic path between the input port (flow in) and a second differential detection point (DP−), a fourth capillary tubing arm (R4) in a fourth hydraulic path between the second differential detection point (DP−) and the output port (flow out), an adjustable mechanical flow restrictor (20) in one of the first, second, third, and fourth hydraulic paths, wherein the adjustable mechanical flow restrictor (20) is operative to mechanically adjust a resistance to flow of a fluid while the fluid flows through the adjustable mechanical flow restrictor.

A capillary bridge viscometer, comprises an input port (flow in) an output port (flow out) a first capillary tubing arm (R1) in a first hydraulic path between the input port and a first differential detection point (DP+), a second capillary tubing arm (R3) in a second hydraulic path between the first differential detection point (DP+) and the output port (flow out), a third capillary tubing arm (R2) in a third hydraulic path between the input port (flow in) and a second differential detection point (DP−), a fourth capillary tubing arm (R4) in a fourth hydraulic path between the second differential detection point (DP−) and the output port (flow out), an adjustable mechanical flow restrictor (20) in one of the first, second, third, and fourth hydraulic paths, wherein the adjustable mechanical flow restrictor (20) is operative to mechanically adjust a resistance to flow of a fluid while the fluid flows through the adjustable mechanical flow restrictor.

Methods for preform and tube draw based on controlling forming zone viscosity determined by calculating a holding force exerted by the glass component in the forming zone on the strand being drawn below. The holding force may be calculated by determining a gravitational force applied to the strand and a pulling force applied to the strand by a pulling device, where the holding force is equal to the opposite of the algebraic sum of the gravitational and pulling forces. The holding force may also be calculated by measuring a stress-induced birefringence in the strand at a point between the forming zone and the pulling device, determining an amount of force applied to the strand at the point corresponding to the birefringence, and calculating the holding force by correcting the amount of force for a gravitational effect of the weight of the strand between the forming zone and the point.