Flow and heat transfer simulation of injection molding with microstructures

Injection molding has been used for mass production of polymer products with microstructures. Conventional Hele‐Shaw 2.5D midplane simulation is unable to describe the flow pattern correctly. It tends to over‐predict the effects of microstructures on global flow patterns. For the unidirectional flow, an x‐z planar based on the general momentum equation is able to achieve better accuracy and to retrieve more detailed flow and heat transfer information around the microstructures. A hybrid numerical technique is developed, which can significantly reduce the nodes and computation time, and yet provide good flow simulation around the microstructures. The mold‐melt heat transfer coefficient and injection speed are shown to be very important factors in determining the filling depth in microstructures. A decrease of the heat transfer coefficient and the occurrence of wall‐slip are likely in microchannels. Polym. Eng. Sci. 44:1866–1876, 2004. © 2004 Society of Plastics Engineers.     

Steel Desulphurisation and Sulphur Bonding in Solidified Ladle Slags

It was investigated in which form sulphur is bonded in ladle slags. For this purpose, the mineralogical phases of the ladle slags were qualitatively and quantitatively evaluated by means of a microprobe. This slag characterisation allowed reconstructing the bonding of sulphur into the phases of the ladle slag. Moreover, the reaction process with regard to the ionic theory as well as the structural formula for the mechanism of sulphur bonding were discussed. The bonding of sulphur into calcium aluminate slags is determined by the sulphide ion content in the slag as well as by the ratio of (CaO)/(Al₂O₃). Calcium sulphide separates only if the slag contains a large number of sulphide ions. When Ca₁₂Al₁₄O₃₃ is separated the sulphide ion is successively integrated into the lattice. The crystal lattice of Ca₁₂Al₁₄O₃₃ is characterised by an open, three‐dimensional anionic network composed of aluminium‐oxygen tetrahedrons linking the edges. In this network, large interstitial spaces are formed, which may be filled with calcium ions on the one hand and statistically with a free oxygen or sulphide ion on the other hand.     

Age-related changes in the metabolism of cholesterol in rat liver microsomes

The effects of aging on the hepatic metabolism of cholesterol were studied in 1-, 6- and 24-month-old male Sprague-Dawley rats. Microsomal 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity, which regulates cholesterol biosynthesis, decreased from 835±144 (SEM) pmol/min/mg protein in the youngest group to 219±34 and 205±53 pmol/min/mg protein (p<0.001) in the 6- and 24-month-old groups, respectively. Cholesterol 7α-hydroxylase activity, which governs bile acid synthesis, was gradually reduced from 70±14 pmol/min/mg protein in the 1-month-old group to 32±7 and 16±3 pmol/min/mg protein (p<0.05) in the 6- and 24-month-old groups, respectively. Acyl coenzyme A:cholesterol acyltransferase activity, which catalyzes the esterification of cholesterol, averaged 431±47 and 452 ±48 pmol/min/mg protein in the 1- and 6-month-old groups, respectively, and was increased to 585±55 pmol/min/mg protein (p<0.05) in the 24-month-old group. The level of total cholesterol showed an age-related increase from 1.56±0.16 mg/g liver in the 1-month-old group to 1.70±0.15 and 2.20±0.19 mg/g liver (p<0.05) in the 6- and 24-month-old groups, respectively. The increase was mainly caused by an accumulation of esterified cholesterol. We conclude that a marked decrease in HMG-CoA reductase occurs between 1 and 6 months of age; thereafter the enzyme activity stays unchanged. The activity of cholesterol 7α-hydroxylase decreases progressively and drastically with age, whereas the capacity for esterifying cholesterol increases slightly. We speculate that the reduced conversion of cholesterol to bile acids may be one explanation of the age-related increase of plasma cholesterol seen in rats.     

A meta-analysis of outcome studies comparing bona fide psychotherapies: Empiricially, "all must have prizes."

This meta-analysis tested the Dodo bird conjecture, which states that when psychotherapies intended to be therapeutic are compared, the true differences among all such treatments are 0. Based on comparisons between treatments culled from 6 journals, it was found that the effect sizes were homogeneously distributed about 0, as was expected under the Dodo bird conjecture, and that under the most liberal assumptions, the upper bound of the true effect was about .20. Moreover, the effect sizes (a) were not related positively to publication date, indicating that improving research methods were not detecting effects, and (b) were not related to the similarity of the treatments, indicating that more dissimilar treatments did not produce larger effects, as would be expected if the Dodo bird conjecture was false. The evidence from these analyses supports the conjecture that the efficacy of bona fide treatments are roughly equivalent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dynamische Belastungen von Zyklonabscheidern bei Anwendung in Blowdown-Systemen

Transient Loading of Cyclone Separators on Use in Blowdown Systems. On use of cyclone separators for phase separation in blowdown systems, pressure-discharge systems, and flaring units, considerable momentary liquid forces are often encountered. Only few details are known about the transient loading and dimensioning of such systems. Thus the behaviour of the entering surge of liquid and its effect on cyclone separators has now been studied experimentally and theoretically. Water/glycerol mixtures of various viscosities were used in these model experiments. After entering the separator the liquid immediately forms a compact wall film. It rapidly expands sideways under the action of the centrifugal force and simultaneously decelerates. A two-dimensional planar mathematical model serves for stepwise calculation of the experimental results with regard to film extension, deceleration, and the resulting transient forces. The results are summarised in the form of design criteria.     

Statistische Sicherheit bei der Modalanalyse von Werkzeugmaschinen

Zusammenfassung Bei der experimentellen Modalanalyse von Maschinen führen Fehler der Frequenzgangmessung und die getroffenen Annahmen bei der Formulierung der elastomechanischen Gleichungen zu Abweichungen zwischen gemessenen und modellierten Frequenzg?ngen. Im vorliegenden Beitrag wird ein auf einer linearen Modellierung beruhendes Frequenzbereichsverfahren diskutiert, das eine Absch?tzung der statistischen Unsicherheiten der dynamischen Modellparameter Eigenfrequenz, D?mpfung und Schwingungsform erlaubt. Es wird gezeigt, da? bei der Relativerregung eine andere Gleichung für die Parametersch?tzung zu w?hlen ist, als bei der absoluten Erregung von Maschinen. Wird die Relativerregung im Modell nicht berücksichtigt, treten erhebliche Fehler bei Ermittlung der Schwingungsformen auf, die exemplarisch diskutiert werden. Der vorgestellte Bericht ist aus den Arbeiten des von der Deutschen Forschungsgemeinschaft (DFG) gef?rderten Sonderforschungsbereiches 121 „Ger?usch- und Schwingungsvorg?nge an Maschinen” hervorgegangen     

Statisches und dynamisches Werkzeugverhalten beim Innenrundschleifen mit axial vorgespannten Werkzeugen

Zusammenfassung Die in diesem Beitrag vorgestellten theoretischen Betrachtungen zum statischen und dynamischen Werkzeugverhalten beim Innenrundschleifen langer Bohrungen nach dem ILB-Verfahren haben wichtige Hinweise für das Proze?verhalten ergeben. Durch geeignete Modellbildung kann hiermit der Einflu? unterschiedlicher Werkzeugspezifikationen sowohl auf die statische Nachgiebigkeit der Werkzeuge und damit letztendlich auf den L?ngsformfehler am Bauteil als auch auf das dynamische Verhalten, insbesondere das Auftreten kritischer Resonanzfrequenzen, vorherbestimmt werden. Die analytischen Berechnungen konnten durch praktische Untersuchungen verfiziert werden. Durchgeführte Schleifversuche haben die Eignung des ILB-Verfahrens als Alternative zur konventionellen Innenrundbearbeitung langer Bohrungen in keramischen Bauteilen best?tigt. Zukünftige Untersuchungen am IFW werden sich auch mit dem Innenrundschleifen langer Bohrungen in Bauteilen aus Hartmetall und geh?rtetem Stahl befassen. Dipl.-Ing.W. Buchholz und Dipl.-Ing.U. Wasmann, wissenschafliche Mitarbeiter des IFW.     

Indicators of Client Engagement: Influences on Alcohol Treatment Satisfaction and Outcomes.

This investigation explored the relationship of client engagement variables (client expectations, therapeutic/working alliance, and session attendance) with treatment satisfaction and posttreatment drinking-related outcomes using data from 2 outpatient alcohol treatment studies (N = 208). Path analysis was used to test a model in which engagement variables jointly influence client satisfaction with treatment and subsequent drinking-related outcomes. The proposed model fit well with the data and accounted for 14-23% of the variance in posttreatment outcomes. The relationships in the model suggest that the link between treatment satisfaction and outcome is clarified by examining client engagement variables, which relate indirectly to outcome by means of client satisfaction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)