Production Equations for Unsteady-State Construction Processes

The production equation called Little’s law has been applied to construction data recently. However, Little’s law was derived for steady-state conditions assuming constant input and output rates and long production runs. Production in construction is inherently temporary, and learning curves and environmental influences often render input and output rates unequal and nonlinear. Starting with a conservation of mass formulation, general equations for work-in-process and cycle time for unsteady-state conditions and limited run production are developed. The motivation behind these equations is to explain common trends in production variables seen on construction projects. Previous studies have shown that when output from a construction production system is drastically increased, a significant upward impact is also seen on cycle time and work-in-process, and this work provides underlying theory and equations to explain these trends. Cycle time and work-in-process equations are presented as functions of time and on average. Data from construction activities are used to show that unsteady-state conditions commonly occur. Reasonable simplifications of the general equations provide guidelines for buffer sizing and resource allocation decisions.     

Childhood sex-typed behavior and sexual orientation: A conceptual analysis and quantitative review.

This article reviewed research examining the association between childhood sex-typed behavior and sexual orientation. Prospective studies suggest that childhood cross-sex-typed behavior is strongly predictive of adult homosexual orientation for men; analogous studies for women have not been performed. Though methodologically more problematic, retrospective studies are useful in determining how many homosexual individuals displayed cross-sex behavior in childhood. The relatively large body of retrospective studies comparing childhood sex-typed behavior in homosexual and heterosexual men and women was reviewed quantitatively. Effect sizes were large for both men and women, with men's significantly larger. Future research should elaborate the causes of the association between childhood sex-typed behavior and sexual orientation and identify correlates of within-orientation differences in childhood sex-typed behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Patterns of symptomatic recovery in psychotherapy.

Using the psychotherapy dosage model in which effect was probability of recovery, this study compared treatment response rates for psychological symptoms. Symptom checklists were administered to 854 psychotherapy outpatients at intake and during treatment. 62 symptoms were grouped into 3 classes on the basis of probit analysis results. Chronic distress symptoms demonstrated the fastest average response rate, whereas characterological symptoms demonstrated the slowest. Acute distress symptoms showed the highest average percentage of patients recovered across doses. A typical outpatient needed about a year of psychotherapy to have a 75% chance of symptomatic recovery. The model holds promise for establishing guidelines for the financing of psychotherapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Measurement of the density and surface tension of Ni-based superalloys in the liquid and mushy states

The densities of three Ni-based superalloys have been measured in both liquid and mushy states by both a modified sessile drop method (MSDM) and a modified pycnometric method (MPM) for alloys CMSX-4 and CM186LC, and for CMSX-10 alloy by MSDM only. The surface tensions of liquid CMSX-4, CM186LC, and CMSX-10 superalloys were measured using the sessile drop method. All measurements were carried out in a highly purified argon atmosphere with the oxygen partial pressure of less than 10⁻¹⁹ MPa in the gas outlet. The densities of all superalloys in both liquid and mushy states were found to decrease with increasing temperature. The volume thermal expansion of each superalloy in the mushy state was found to be higher than that in the liquid state. The densities determined by different methods have been critically assessed and recommended values in both liquid and mushy states are given as a linear function of temperature for the three Ni-based superalloys. The surface tension of liquid CMSX-4 superalloy was found to decrease with increasing temperature, while that of liquid CMSX-10 superalloy increases with increasing temperature. The wetting behavior of liquid CM186LC on the alumina substrate was found (1) to differ significantly from that of CMSX-4 and CMSX-10 and (2) to vary with time. A HfO₂-rich layer was found in the contact area of CM186LC with the alumina substrate, which could lead to some uncertainty in the value obtained for the surface tension determined for CM186LC.     

Effects of labor contractions on catecholamine release and breathing frequency in newborn rats.

Plasma catecholamines in newborn rats (0-2 hr old) were analyzed following vaginal birth, cesarean section with simulated labor contractions, or cesarean section without labor contractions. Upon delivery, pups were exposed to key elements of the rat's natural birth process, that is, umbilical cord occlusion, tactile stimulation, and cooling. Only pups exposed to actual or simulated labor showed an immediate rise in norepinephrine and epinephrine. Initial postpartum respiratory frequencies were higher in vaginal than in cesarean delivered pups and, in all groups, inversely correlated with catecholamine titers, suggesting respiratory distress or transient tachypnea at lower catecholamine levels. These findings establish a rat model for analyzing effects of labor on neonatal adaptive response during the transition from prenatal to postnatal life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On-line studies and computer simulation of the melt spinning of nylon-66 filaments

A mathematical model was developed to describe the high-speed melt-spinning behavior crystallizable polymers. This model included the effects of acceleration, gravity, and air friction on the kinematics of the process; temperature and molecular orientation on the crystallization kinetics of the polymer; and temperature, molecular weight, and crystallinity on the elongational viscosity of the material. Experimental on-line diameter, birefringence, and temperature profiles were obtained for a 12,000 Mn nylon-66 at 2.5 g/min spun at take-up speeds ranging from 2800 to 6600 m/min. These profiles were qualitatively and reasonably quantitatively in agreement with the predicted profiles. They indicated that orientation induced crystallization occurs at spinning speeds greater than 4000 m/min. The experimental diameter and birefringence profiles were compared to those predicted by the model using Avrami indices of 3, 2, and 1. There was a small increase in the crystalline index at the lower speeds with decreasing index. The effect of the strain hardening was more significant at the higher speeds, this being shown by decreasing the exponent in the relationship for the crystallinity on the elongational viscosity. The model developed in this study indicates that high spinning speeds provide the high stress environment that increases the molecular orientation within the fiber. It is this higher molecular orientation that is the driving force for rapid crystallization on the spinline. This rapid crystallization causes a strain hardening, preventing any further drawdown in the fiber diameter and an abrupt rise in the birefringence. This behavior closely corresponds to the observed spinline profiles.     

Theoretical examination of the mechanism of aldose-ketose isomerization

Two mechanisms for an aldose–ketose isomerization havebeen examined using high level ab initio and semiempirical molecularorbital methods. The proton transfer pathway via an enediolintermediate is shown to be favored in the absence of a metalion, while the hydride transfer pathway becomes favored in thepresence of a metal ion. Our calculations explain why the protontransfer pathway is operative in most aldose–ketose isomerizationreactions. These calculations also provide further support forthe previously proposed metal ion-mediated hydride transfermechanism for xylose isomerase.