Enhanced Hydrothermal Resistance of Y‐TZP Ceramics Through Colloidal Processing

Two commercial zirconia powders with 3 mol% of yttria (TZ3YE and TZ3YS, labeled as ZE and ZS, respectively) supplied by Tosoh (Japan) were used for this study. Maximum colloidal stability for ZE was achieved by dispersing the powders in a mixture of water/ethanol of 90:10 (wt/wt) using a sonication probe. The rheological behavior of the suspensions was optimized in terms of solids content ranging from 20 to 33 vol% and sonication time (0–6 min), the best results being obtained after 2 min. ZS samples were prepared to a solids loading of 30 vol% in water dispersing with 2 min‐sonication. Samples obtained by slip casting in plaster molds were used for dynamic sintering studies, and fully dense and nanostructured specimens were obtained at temperatures of 1300°C–1350°C (ZE samples) and 1400°C per 2 h (ZS samples). The Hardness (H) and Young's Modulus (E) properties of the specimens were studied by nanoindentation technique giving 17 and 250 GPa mean values for H and E, respectively. The specimens were then forced to a low‐temperature degradation (LTD) treatment at 130°C for 240 h in steps of 60 h. Raman spectroscopy and nanoindentation results of hydrothermally treated samples showed the absence of transformation from tetragonal to monoclinic phase until 180 h whereas the mechanical properties maintained constant even at the sample surface. After 240 h of LTD, the monoclinic phase was detected on all specimens by Raman peaks centered at 180, 191, and 383 cm^?1. The nanoindentation study revealed an important loss of mechanical features reaching 10 and 175 GPa for H and E, respectively. In the case of the ZS specimens, no monoclinic phase is detected after 240 h of LTD treatment and no decay of E or H is detected. The free defect microstructure reached for the ZS specimen revealed a higher hydrothermal resistance so that it is concluded that the excellent behavior against thermal degradation is possible due to the large uniformity obtained by colloidal processing rather than the particle size of the starting powders.     

Analysis of Tribological Performance of Cu Hybrid Composites Reinforced with Graphite and TiC Using Factorial Techniques

In this study, a copper hybrid metal matrix composite reinforced with graphite (5, 10, and 15 vol%) and TiC (5, 10, and 15 vol%) was processed by a powder metallurgy route. Optical micrographs confirm the uniform distribution of reinforcements in the copper matrix. The hardness of the composites decreased with the addition of graphite. However, the addition of TiC into the copper matrix increased the hardness of the composites due to its high hardness. The influence of graphite percentages, load, sliding speed, and sliding distance on the wear of the as-sintered hybrid composites was studied based on the design of experiments. Analysis of variance (ANOVA) was used to study the effect of the parameters on the wear weight loss of the hybrid composites. The weight loss due to wear of the hybrid composites decreases from 0.1345 to 0.0830 g as the volume percentage of graphite increases from 5 to 15%. Results indicated that the normal load has greater static influence of 43.85%, sliding distance has an influence of 29.84%, percentage of graphite has an influence of 15.17%, and sliding speed has an influence of 1.83% on the weight loss of copper hybrid composites due to sliding wear. The worn-out surfaces were analyzed using electron microscopy, which reveals that the addition of both hard ceramic reinforcement TiC and soft solid lubricant graphite significantly improves the tribological performance of the copper composites.     

Using alloy to analyse a spatio-temporal access control model supporting delegation

Pervasive computing applications use the knowledge of the environment to provide better services and functionality to the end user. Access control for such applications needs to use contextual information. Towards this end, we proposed an access control model based on role-based access control that uses the environmental contexts time and location to determine whether a user can get access to some resource. The model also supports delegation which is important for dynamic applications where a user is unavailable and permissions may have to be transferred temporarily to another user/role in order to complete a specific task. Such a model typically has numerous features to support the requirements of various applications. The features may interact in subtle ways to produce conflicts. Here, we propose an automated approach using Alloy for detecting such conflicts. Alloy is supported by a software infrastructure that allows automated analysis of models and has been used to verify industrial applications. The results obtained from the analysis will enable the users of the model to make informed decisions.     

Gender differences in acute alcohol effects on self-regulation of arousal in response to emotional and alcohol-related picture cues.

Basic mechanisms through which men and women self-regulate arousal have received little attention in human experimental addiction research, although stress-response-dampening and craving theories suggest an important role of emotional arousal in motivating alcohol use. This study examined gender differences in the effects of acute alcohol intoxication on psychophysiological and self-reported arousal in response to emotionally negative, positive, and neutral, and alcohol-related, picture cues. Thirty-six social drinkers (16 women) were randomly assigned to an alcohol, placebo, or control beverage group and exposed to picture cues every 10 s (0.1 Hz presentation frequency). Psychophysiological arousal was assessed via a 0.1-Hz heart rate variability (HRV) index. A statistically significant beverage group-by-gender interaction effect on psychophysiological, but not self-reported, arousal was found. The 0.1-Hz HRV responses to picture cues were suppressed by alcohol only in men. This gender-specific suppression pattern did not differ significantly across picture cue types. There were no significant gender differences in the placebo or control group. Greater dampening of arousal by alcohol intoxication in men, compared with women, may contribute to men’s greater tendency to use alcohol to cope with stress. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimization of friction stir welding parameters for dissimilar aluminum alloys

Assembly consisting of cast and wrought aluminum alloys has wide spread application in defense and aero space industries. For the efficacious use of the transition joints, the weld should have adequate strength and formability. In the present investigation, A356 and 6061 aluminum alloys were friction stir welded under tool rotational speed of 1000–1400 rpm and traversing speed of 80–240 mm/min, keeping other parameters same. The variable process window is responsible for the change in total heat input and cooling rate during welding. Structural characterization of the bonded assemblies exhibits recovery-recrystallization in the stirring zone and breaking of coarse eutectic network of Al–Si. Dispersion of fine Si rich particles, refinement of 6061 grain size, low residual stress level and high defect density within weld nugget contribute towards the improvement in bond strength. Lower will be the tool rotational and traversing speed, more dominant will be the above phenomena. Therefore, the joint fabricated using lowest tool traversing and rotational speed, exhibits substantial improvement in bond strength (∼98% of that of 6061 alloy), which is also maximum with respect to others.     

A sensitive magnetic field sensor using BPSCCO thick film

A highly sensitive magnetic sensor operating at liquid nitrogen temperature and based on BPSCCO screen-printed thick film, is reported. The sensor resistance for an applied magnetic field of 100 ×10⁻⁴ T (100 gauss) exhibits an increase by 360% of its value in zero field at 77.4 K. The performance of the sensor in presence of magnetic field, the hysteretic features and the effect of thermal cycling, has been discussed.     

MSXmin: a modular multicast ATM packet switch with low delay andhardware complexity

We propose and analyze the architecture for a large-scale high-speed multicast switch called MSXmin. The hardware complexity of MSXmin is O(N log² N) which compares favorably with existing architectures. Further, the internal latency of the MSXmin is O(log² N) bits. While it is superior to the existing architectures in terms of the hardware complexity and the internal latency, it is comparable to other multicast switches in terms of the header overhead and translation table complexity. MSXmin is output buffered and based on the group knockout principle. Moreover, MSXmin is a dual-bit-controlled tree-based switch     

Gephyrin-Lacking PV Synapses on Neocortical Pyramidal Neurons

Gephyrin has long been thought of as a master regulator for inhibitory synapses, acting as a scaffold to organize γ-aminobutyric acid type A receptors (GABA_ARs) at the post-synaptic density. Accordingly, gephyrin immunostaining has been used as an indicator of inhibitory synapses; despite this, the pan-synaptic localization of gephyrin to specific classes of inhibitory synapses has not been demonstrated. Genetically encoded fibronectin intrabodies generated with mRNA display (FingRs) against gephyrin (Gephyrin.FingR) reliably label endogenous gephyrin, and can be tagged with fluorophores for comprehensive synaptic quantitation and monitoring. Here we investigated input- and target-specific localization of gephyrin at a defined class of inhibitory synapse, using Gephyrin.FingR proteins tagged with EGFP in brain tissue from transgenic mice. Parvalbumin-expressing (PV) neuron presynaptic boutons labeled using Cre- dependent synaptophysin-tdTomato were aligned with postsynaptic Gephyrin.FingR puncta. We discovered that more than one-third of PV boutons adjacent to neocortical pyramidal (Pyr) cell somas lack postsynaptic gephyrin labeling. This finding was confirmed using correlative fluorescence and electron microscopy. Our findings suggest some inhibitory synapses may lack gephyrin. Gephyrin-lacking synapses may play an important role in dynamically regulating cell activity under different physiological conditions.     

Prediction of fatigue life with interspersed mode-I and mixed-mode (I and II) overloads by an exponential model: Extensions and improvements

The current work is an extension of the authors’ earlier work and presents a life prediction methodology under interspersed mode-I and mixed-mode (I and II) overloads. The important controlling parameter in the model is ‘specific growth rate’ (m). It depends on two crack driving forces i.e. stress intensity factor range and maximum stress intensity factor as well as material parameters i.e. fracture toughness, Young’s modulus, and yield stress. The dependence of ‘m’ on these parameters is correlated through a dimensionless parameter ‘l’. It is observed that the present model predicts the end life of post-overload period well in case of 7020 T7 and 2024 T3 Al-alloys.