Metal powder compacting dies: optimised design by analytical or numerical methods

Abstract

The initial data needed to design metal powder compaction die are: compact shape and density, powder mix composition, compaction and radial pressure, part number and tool materials. The design targets are: diameters of insert and ring, sometimes number of rings and interference or interferences. The constraints include: no tensile stresses on the insert, no risk of relative motion at part ejection, no unwanted alteration of material microstructures and maximum stresses always below the allowable limits. Usually the design is based on engineering experience, company knowhow, and approximated analytical calculations and cost considerations.

This study is focused on the use of numerical methods to determine the design parameters of dies for powder compaction. Both room temperature and warm compaction have been investigated. Numerical algorithms, implemented into FEM calculation codes, enable one to optimise the common diameter of insert and ring, corresponding to the lowest stresses on both items, or to find the minimum value of the outer diameter. A wide range of compaction pressures, die materials and geometries, interferences and allowable stresses have been explored. To compare the results, based either on analytical or numerical methods, circular dies have been investigated. The differences among the results depend on the consideration of the actual stressed length, or compact height, and total die length. The calculations by analytical methods overestimate the stresses. The paper presents some suitable nomograms for the comparison of results of calculations performed either by Laméformulas or by sophisticated numerical methods.     

From task force to statute: establishing health sciences libraries in state law as a component of the health care system

This paper includes a report on a case of prosthetic valve endocarditis due to Micrococcus luteus and a review of the sixteen cases of endocarditis due to Micrococcus species reported in the literature. The patient was successfully treated with rifampicin combined for two weeks with gentamicin and vancomycin and for another four weeks with teicoplanin. The hospital course was uneventful and no surgery was required.     

From acclaim to blame: Evidence of a person sensitivity decision bias.

In a series of studies, the authors established empirical support for a general decision-making bias that they termed a person sensitivity bias. Specifically, a person sensitivity bias consists of a person positivity bias (D. O. Sears, 1983) under positive performance conditions and a person negativity bias under negative performance conditions. The authors conducted the first empirical studies of a direct comparison between individuals and objects performing the same task under both positive and negative performance conditions. Two additional studies tested the boundaries of the sensitivity bias within negatively framed decision dilemmas. The results are discussed in terms of their relevance toward a more comprehensive theory of person-object evaluation differences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

From the Grave to the Cradle: Evidence That Mortality Salience Engenders a Desire for Offspring.

On the basis of terror management theory, the authors hypothesized that reminders of mortality (mortality salience) should promote the desire for offspring to the extent that it does not conflict with other self-relevant worldviews that also serve to manage existential concerns. In 3 studies, men, but not women, desired more children after mortality salience compared with various control conditions. In support of the authors' hypothesis that women's desire for offspring was inhibited as a function of concerns about career success, Study 3 showed that career strivings moderated the effect of mortality salience on a desire for offspring for female participants only; furthermore, Study 4 revealed that when the compatibility of having children and a career was made salient, female participants responded to mortality salience with an increased number of desired children. Taken together, the findings suggest that a desire for offspring can function as a terror management defense mechanism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

From adolescence to adulthood: Age-related changes in beliefs about cigarette smoking in a Midwestern community sample.

The current study used a cohort-sequential design to examine age-related changes in health-relevant beliefs from the middle school years through age 37 in a large, midwestern, community sample (N?=?8,556). Results suggest systematic age-related changes such that beliefs in the personalized risks of smoking declined in middle school and then increased, beliefs in generalized health risks increased beginning in the middle school years, and values placed on health as an outcome decreased in the high school years and then increased. These findings suggest that intervention programs must counter declining personalized risk perceptions among middle school students and declining values placed on health among high school age students, (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

From waste to wealth: recycling the secondary resource from steel ladle as a flux in Si-killed steelmaking process

With the regulations pertaining to the environment and waste disposal becoming stringent day by day, the steelmaking industry is being compelled to adopt a zero-waste-policy for sustainability. As a consequence, 3R (reduce, reuse and recycle) technique of waste handling has become the most favoured option among the industries. This paper focuses on recycling of slag generated after secondary refining process. Trials were conducted in two stages, namely (a) prevention of dusting phenomenon of Al-killed steel ladle slag to generate lump slag by suitably selecting the ladle covering compound and chemically modifying the slag, and (b) utilisation of the lump slag as a 100% replacement of synthetic slag in Si-killed steel ladles, leading to a reduction in its specific consumption from 1.2?kg/TLS to zero. As a process requirement, specific power consumption, arcing time and degree of desulphurisation were considered as the major parameters for comparing the results using hypothesis test statistical tool.     

Review of Neurophilosophy of free will: From libertarian illusions to a concept of natural autonomy.

Reviews the book, Neurophilosophy of free will: From libertarian illusions to a concept of natural autonomy by Henrik Walter and C. Klohr (2001). In this book, Henrik Walter applies the methodology of neurophilosophy to one of philosophy’s central challenges and enduring questions: the notion of free will. The author argues that free will is an illusion if we mean by it that under identical conditions we would be able to do or decide otherwise, while simultaneously acting only for reasons and being the true originators of our actions. In place of this problematic version of free will, Walter offers what he calls “natural autonomy,” that is, self-determination unaided by supernatural powers that could exist even in an entirely determined universe. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Using Taxometric Analysis to Distinguish a Small Latent Taxon From a Latent Dimension With Positively Skewed Indicators: The Case of Involuntary Defeat Syndrome.

Joining the debate on the structure of depression, S. R. H. Bearh and N. Amir (2003) analyzed college students' responses to 6 Beck Depression Inventory (BDI) items with predominantly somatic content and concluded that they identified a small latent taxon corresponding to involuntary defeat syndrome. An exact replication of these analyses yielded virtually identical taxometric results, but parallel analyses of simulated taxonic and dimensional comparison data matching the intercorrelations and skewed distributions of the BDI items showed the results to be more consistent with dimensional than with taxonic latent structure. Analyses in a clinical sample with nonskewed indicators further supported a dimensional interpretation. The authors discuss methodological strategies for conducting and interpreting taxometric analyses under the adverse conditions commonly encountered in psychopathology research, including skewed indicators and small putative taxa. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reduced Stroop Interference for Opponent Colors May Be Due to Input Factors: Evidence From Individual Differences and a Neural Network Simulation.

Sensory or input factors can influence the strength of interference in the classic Stroop color-word task. Specifically, in a single-trial computerized version of the Stroop task, when color-word pairs were incongruent, opponent color pairs (e.g., the word BLUE in yellow) showed reduced Stroop interference compared with nonopponent color pairs (e.g., BLUE in red). In addition, participants' color discrimination ability was measured by standard color vision tests (i.e., Farnsworth-Munsell 100-Hue Test and Ishihara plates). Error rates in the Farnsworth-Munsell test correlated positively with the amount of Stroop interference. Neural network simulations (variants of J. D. Cohen, K. Dunbar, & J. L. McClelland's, 1990, model) showed that only a distributed trichromatic input layer was able to simulate these findings. Thus, sensory input from the color system needs to be incorporated into current accounts of the Stroop effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Suboptimal Exposure to Facial Expressions When Viewing Video Messages From a Small Screen: Effects on Emotion, Attention, and Memory.

The authors examined the effects of suboptimally presented facial expressions on emotional and attentional responses and memory among 39 young adults viewing video (business news) messages from a small screen. Facial electromyography (EMG) and respiratory sinus arrhythmia were used as physiological measures of emotion and attention, respectively. Several congruency priming effects were found. In particular, happy facial primes prompted increased (a) pleasure ratings, (b) orbicularis oculi EMG activity, (c) perceived trustworthiness, and (d) recognition memory for video messages with a positive emotional tone. Emotional and other responses to video messages presented on a small screen can be modified with suboptimal affective primes, but even small differences in the emotional tone of the messages should be allowed for. (PsycINFO Database Record (c) 2010 APA, all rights reserved)