Nonlinear models of chatter in drilling processes

We develop a nonlinear model of chatter in drilling that incorporates friction of the material on the cutting tool and its interaction with the axial-torsional mode of vibration seen in twist drills. Stability criteria are determined for both regenerative and non-regenerative chatter, and the effect of tool parameters and the friction law itself on the results is analysed. Our analysis shows that the exact form of the friction law is not critical in the stability calculation, only the size of the friction coefficient for steady cutting, and the slope of the friction law at the steady cutting state. However, its interaction with the geometry of the vibration is crucial. In the laboratory, drilling vibrational instabilities can occur at frequencies less than the natural frequency of the excited mode of the drill, and we find this result depends critically on the shape of the vibration mode projected onto the cutting edge of the drill.     

Missing information in selection: An application of the Einhorn-Hogarth ambiguity model.

This article argues that the devaluation of options with missing information, found in previous research, is a specific example of ambiguity avoidance in choice. H. J. Einhorn and R. M. Hogarth's (see record 1986-13621-001) ambiguity model was used to make predictions concerning responses to missing information in an employee-selection context. A within-subjects design was used to test the hypothesis that decision makers would avoid options with missing information when they were anticipating gain, but they would prefer such options when they were anticipating loss. Degree of ambiguity was expected to interact with this effect. The results supported the hypothesized effect of decision-maker perspective on choice. However, although there was a significant interaction between decision-maker perspective and degree of ambiguity, it was not of the nature that was predicted by the Einhorn-Hogarth model. Generalized pessimism was negatively correlated with preferences for missing-information options. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

See what you want to see: Motivational influences on visual perception.

People's motivational states--their wishes and preferences--influence their processing of visual stimuli. In 5 studies, participants shown an ambiguous figure (e.g., one that could be seen either as the letter B or the number 13) tended to report seeing the interpretation that assigned them to outcomes they favored. This finding was affirmed by unobtrusive and implicit measures of perception (e.g., eye tracking, lexical decision tasks) and by experimental procedures demonstrating that participants were aware only of the single (usually favored) interpretation they saw at the time they viewed the stimulus. These studies suggest that the impact of motivation on information processing extends down into preconscious processing of stimuli in the visual environment and thus guides what the visual system presents to conscious awareness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exploiting Covalency to Enhance Metal–Oxide and Oxide–Oxide Adhesion at Heterogeneous Interfaces

We employ first-principles density functional calculations to explore atomic-level interactions and predict the ideal work of adhesion at the SiO₂/nickel and ZrO₂/SiO₂ interfaces. We find that chemical bonding at the interface serves to strengthen significantly interfaces formed with SiO₂, which exhibits significant covalent bonding character, relative to those formed using more ionic oxides, such as Al₂O₃, in place of SiO₂. The improved strength of these interfaces due to local bonding interactions may hold materials design implications for practical applications that require optimal adhesion between metal-ceramic layered structures, including thermal barrier coatings.     

Personality and substance dependence symptoms: Modeling substance-specific traits.

Personality traits related to neuroticism and disinhibition have been consistently associated with substance use disorders (SUDs). It is unclear, however, whether different personality traits predict distinct forms of substance dependence. Additionally, it is unclear whether personality traits continue to predict alcohol, drug, and tobacco dependence after controlling for comorbid antisociality and other SUDs. The current study addresses these questions by characterizing relations between personality traits and substance dependence symptoms in a longitudinal sample of 3,720 college students. Results revealed that antisociality and certain core personality traits predicted multiple types of substance pathology. In addition, several personality traits were differentially associated with alcohol, drug, and tobacco symptomatology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Equity and the City: The Case of the East Perth Redevelopment

This article examines the Commonwealth Government's urban planning initiative, the Building Better Cities Program, as it was implemented in the East Perth redevelopment. It analyses the disparity between one of the Program's key objectives, improved social justice, and the outcomes evident in East Perth. The nature of Commonwealth-State relations is examined to reveal that the tensions inherent in a federal polity are a cause of the redevelopment failing to achieve the objective of improved social justice outcomes.     

Humidity‐Triggered Self‐Healing of Microporous Polyelectrolyte Multilayer Coatings for Hydrophobic Drug Delivery

Layer‐by‐layer (LbL) self‐assemblies have inherent potential as dynamic coatings because of the sensitivity of their building blocks to external stimuli. Here, humidity serves as a feasible trigger to activate the self‐healing of a microporous polyethylenimine/poly(acrylic acid) multilayer film. Microporous structures within the polyelectrolyte multilayer (PEM) film are created by acid treatment, followed by freeze‐drying to remove water. The self‐healing of these micropores can be triggered at 100% relative humidity, under which condition the mobility of the polyelectrolytes is activated. Based on this, a facile and versatile method is suggested for directly integrating hydrophobic drugs into PEM films for surface‐mediated drug delivery. The high porosity of microporous film enables the highest loading (≈303.5 μg cm^?2 for a 15‐bilayered film) of triclosan to be a one‐shot process via wicking action and subsequent solvent removal, thus dramatically streamlining the processes and reducing complexities compared to the existing LbL strategies. The self‐healing of a drug‐loaded microporous PEM film significantly reduces the diffusion coefficient of triclosan, which is favorable for the long‐term sustained release of the drug. The dynamic properties of this polymeric coating provide great potential for its use as a delivery platform for hydrophobic drugs in a wide variety of biomedical applications.     

Spectroscopic microscopy analysis of the interior pH of individual phospholipid vesicles

The use of phospholipid vesicles as reaction containers, as vehicles for pharmaceutical drug delivery, and as model systems for cells has prompted the development of new methods for analyzing the structure of vesicles and their contents. The pH of the interior of vesicles is of particular interest when analytes are encapsulated and concentrated with the use of a pH gradient. While the interior pH is generally measured for large populations of vesicles, we report the measurement of the interior pH of individual vesicles as their buffer contents are titrated by transfer of N-methylbutylamine (NMBA) into the vesicle by a pH gradient. The initially acidic buffer within the vesicles is titrated along with a small concentration of an encapsulated pH sensitive dye, 5,6-carboxy SNARF-1-dextran. Images of the indicator fluorescence from each vesicle and its dispersed fluorescence spectrum are recorded using epi-illumination spectral fluorescence microscopy. From a fit of the spectra to the respective acid and base forms of the fluorescent indicator, the interior pH of individual vesicles as a function of the concentration of the NMBA titrant in the external solution could be determined.