Constraints on Melt Production Rate Beneath the Mid-ocean Ridges Based on Passive Flow Models

1996 ◽  
pp. 589-620
Author(s):  
Yongshun John Chen
Keyword(s):  
Production Rate ◽  
Flow Models ◽  
Ocean Ridges ◽  
Passive Flow

Steady motion within a curved pipe

1976 ◽  
Vol 347 (1650) ◽  
pp. 345-370 ◽  
Keyword(s):  
Pressure Gradient ◽  
Cross Section ◽  
Steady Motion ◽  
Careful Consideration ◽  
Dean Number ◽  
Curved Pipe ◽  
Boundary Layer Problem ◽  
Flow Models ◽  
Passive Flow ◽  
Secondary Motion

The forcing of fluid through a tube, of uniform cross section (~ a ) and coiled to form an arc of a circle of radius R (≫ a ), by the application of a steady constant pressure gradient along the tube is discussed for large values of the Dean number D . An asymptotic description is presented for the fully-developed laminar flow within a general symmetric section, in which there is outward centrifuging of the secondary motion in the inviscid core, supplemented by a faster viscous return motion near the pipewalls, while the downpipe velocity increases steadily across the core. A similarity solution of the viscous flow, with the associated core flow thereby being determined, is calculated for a triangular cross section, but for a rectangular tube analytical and numerical arguments are put forward that point fairly conclusively to the non-existence of an attached laminar motion, near the inside bend at least, at high Dean numbers. For if the pressure-gradient is imagined to vary like the m th power of distance across the section, then computed results indicate that local solutions of the boundary layer problem can be found only for ( m -1/2). The assertion is backed up by an analytical study for small positive values of ( m -1/2). The dynamical properties in the neighbourhood of a flat outside bend, or of a ‘pinched' inside bend, of a tube also need careful consideration, although these may be essentially passive flow regions and some account of the local features there can be given. Near a flat outside bend two possible flow models arise, depending on the local nature of the coreflow.

Dry chip feedrate control using online chip moisture

TAPPI Journal ◽  
2018 ◽  
Vol 17 (05) ◽  
pp. 295-305
Author(s):  
Wesley Gilbert ◽  
Ivan Trush ◽  
Bruce Allison ◽  
Randy Reimer ◽  
Howard Mason
Keyword(s):  
Production Rate ◽  
Control Strategy ◽  
Rate Control ◽  
Near Infrared ◽  
Dry Mass ◽  
The Other ◽  
Process Variability ◽  
Moisture Sensor ◽  
Feedback Control Strategy ◽  
And Control

Normal practice in continuous digester operation is to set the production rate through the chip meter speed. This speed is seldom, if ever, adjusted except to change production, and most of the other digester inputs are ratioed to it. The inherent assumption is that constant chip meter speed equates to constant dry mass flow of chips. This is seldom, if ever, true. As a result, the actual production rate, effective alkali (EA)-to-wood and liquor-to-wood ratios may vary substantially from assumed values. This increases process variability and decreases profits. In this report, a new continuous digester production rate control strategy is developed that addresses this shortcoming. A new noncontacting near infrared–based chip moisture sensor is combined with the existing weightometer signal to estimate the actual dry chip mass feedrate entering the digester. The estimated feedrate is then used to implement a novel feedback control strategy that adjusts the chip meter speed to maintain the dry chip feedrate at the target value. The report details the results of applying the new measurements and control strategy to a dual vessel continuous digester.

CORTICOSTEROID-UMSATZ UND CORTICOSTEROID-PRODUKTION BEI RATTEN UNTER DER BEHANDLUNG MIT ANABOLEN STEROIDEN

1965 ◽  
Vol 48 (2) ◽  
pp. 263-271 ◽  
Author(s):  
Herbert Schriefers ◽  
Gerlinde Scharlau ◽  
Franzis Pohl
Keyword(s):  
Production Rate ◽  
Adult Female ◽  
Anabolic Steroids ◽  
Reduction Rate ◽  
Female Rats ◽  
Adrenal Weight ◽  
Hydrogenase Activity ◽  
Anabolic Effect ◽  
Liver Slices

ABSTRACT After the administration of anabolic steroids to adult female rats in daily doses of 1 mg per animal for 14 days, the following parameters were investigated: the rate of the Δ4-5α-hydrogenase-catalyzed cortisone reduction in liver slices and microsomal fractions, the adrenal weight and the in vitro corticosterone production rate. Among the steroids tested, only 17α-methyl-testosterone and 17α-ethyl-19-nor-testosterone were effective in lowering significantly cortisone reduction rate by liver slices with concomitant decreases in microsomal Δ4-5α-hydrogenase-activity. Testosterone, 19-nor-testosterone, 17α-ethinyl-19-nor-testosterone, 17α-methyl-17β-hydroxy-androsta-1,4-dien-3-one and 1-methyl-17β-hydroxy-androst-1-en-3-one were ineffective or only slightly effective. Adrenal weight and absolute corticosterone production rate (μg/60 min per animal) were decreased after treatment with 17α-methyl-testosterone, 17α-ethyl-19-nor-testosterone and 1-methyl-17β-hydroxy-androst-1-en-3-one. Corticosterone production was decreased with 17α-ethinyl-19-nor-testosterone in spite of an unchanged adrenal weight. The relative corticosterone production rate (μg/60 min · 100 mg adrenal) was in any cases unaffected. According to these results there exists – with the exception of 17α-ethinyl-19-nor-testosterone – a strict parallelism between corticosteroid turnover and corticosterone production rate: unchanged turnover is correlated with unchanged corticosterone production rate, while a decreased turnover is correlated with decreased adrenal activity. The protein-anabolic effect of certain anabolic steroids may be partly due to an anti-catabolic action of these compounds resulting from a decreased corticosteroid inactivation and production rate. Possible mechanisms by which anabolic steroids may affect corticosteroid-balance are discussed.

VARIATION OF CORTISOL METABOLISM AS A CONTRIBUTING FACTOR TO DISCREPANCIES IN THE MEASUREMENT OF CORTISOL PRODUCTION RATE

1972 ◽  
Vol 70 (1) ◽  
pp. 89-96 ◽  
Author(s):  
M. J. Levell
Keyword(s):  
Production Rate ◽  
Isotope Dilution ◽  
Normal Subjects ◽  
Contributory Factor ◽  
Morning Dose ◽  
Production Rates ◽  
Evening Dose ◽  
Cortisol Metabolism

ABSTRACT Five normal subjects were given [14C] cortisol in the morning and [3H] cortisol in the evening, in both cases by mouth. The excretion of radioactivity in tetrahydrocortisol (THF) and tetrahydrocortisone (THE) was measured by a modified form of reverse isotope dilution. In 2 subjects, the ratio of isotopic THF/isotopic THE was higher after the evening dose than after the morning dose. In 1 subject the ratio decreased. In 2 subjects it did not change. Cortisol production rates calculated from THF were usually higher than those calculated from THE. The observed variations of metabolism were only a contributory factor to these discrepancies.

Avalanche Stratification - Experimental Tests of the “Metastable Wedge” and “Continuous Flow” Models

2000 ◽  
Vol 627 ◽  
Author(s):  
M. E. Swanson ◽  
M. Landreman ◽  
J. Michel ◽  
J. Kakalios
Keyword(s):  
Continuous Flow ◽  
Granular Media ◽  
Experimental Tests ◽  
Coarse Sand ◽  
Angle Of Repose ◽  
Flow Models ◽  
Maximum Angle ◽  
Stratification Effect ◽  
Upward Moving ◽  
Moving Layer

ABSTRACTWhen an initially homogeneous binary mixture of granular media such as fine and coarse sand is poured near the closed edge of a “quasi-two-dimensional” Hele-Shaw cell consisting of two vertical transparent plates held a narrow distance apart, the mixture spontaneously forms alternating segregated layers. Experimental measurements of this stratification effect are reported in order to determine which model, one which suggests that segregation only occurs when the granular material contained within a metastable heap between the critical and maximum angle of repose avalanches down the free surface, or one for which the segregation results from smaller particles becoming trapped in the top surface and being removed from the moving layer during continuous flow. The result reported here indicate that the Metastable Wedge model provides a natural explanation for the initial mixed zone which precedes the formation of the layers, while the Continuous Flow model explains the observed upward moving kink of segregated material for higher granular flux rates, and that both mechansims are necessary in order to understand the observed pairing of segregated layersfor intermediate flow rates and cell separations.

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